ZooKeys 288: 1–213, doi: 10.3897/zookeys.288.4095
Generic revision and species classification of the Microdontinae (Diptera, Syrphidae)
Menno Reemer 1,†, Gunilla Ståhls 2,‡
1 Naturalis Biodiversity Center, European Invertebrate Survey – the Netherlands, P.O. Box 9517, 2300 RA Leiden, the Netherlands
2 Finnish Museum of Natural History, Entomology dept., P.O. Box 17, FIN-00014 University of Helsinki, Finland

Corresponding author: Menno Reemer (menno.reemer@naturalis.nl)

Academic editor: M. Hauser

received 8 October 2012 | accepted 13 February 2013 | Published 12 April 2013


(C) 2013 Menno Reemer. This is an open access article distributed under the terms of the Creative Commons Attribution License 3.0 (CC-BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


For reference, use of the paginated PDF or printed version of this article is recommended.

Abstract

With 552 species group names available (excluding misspellings), the Microdontinae constitute the smallest of the three subfamilies of Syrphidae. Paradoxically, this subfamily is taxonomically the least organized of the three: 388 species names were previously classified in a single genus, Microdon Meigen, 1803. The present paper introduces a new generic classification of the Microdontinae, relying partly on the results of phylogenetic analyses of morphological and molecular data as published in other papers, and partly on examination of primary type specimens of 347 taxa, plus additional material, and original descriptions. A total number of 67 genus group names (excluding misspellings) are evaluated, redescribed, diagnosed and discussed, with several implications for their taxonomic status. Of these, 43 names are considered as valid genera, 7 as subgenera, 17 as synonyms. Two generic names (Ceratoconcha Simroth, 1907, Nothomicrodon Wheeler, 1924) are left unplaced, because they are known from immature stages only and cannot be reliably associated with taxa known from adults. The following 10 new genera are described by Reemer: Domodon, Heliodon, Laetodon, Menidon, Mermerizon, Metadon, Peradon, Piruwa, Sulcodon and Thompsodon. A key to all genera, subgenera and species groups is given. A total number of 26 new species are described in the following genera: Archimicrodon Hull, 1945, Ceratrichomyia Séguy, 1951, Domodon, Furcantenna Cheng, 2008, Heliodon, Indascia Keiser, 1958, Kryptopyga Hull, 1944, Masarygus Brèthes. 1908, Mermerizon, Metadon, Microdon, Paramixogaster Brunetti, 1923, Piruwa, Pseudomicrodon Hull, 1937, Rhopalosyrphus Giglio-Tos, 1891, and Thompsodon. New lectotypes are designated for Ceratrichomyia behara Séguy, 1951 and Microdon iheringi Bezzi, 1910. A total number of 267 new combinations of species and genera are proposed. New synonyms are proposed for 19 species group names. Three replacement names are introduced for primary and secondary junior homonyms: Microdon shirakii nom. n. (= Microdon tuberculatus Shiraki, 1968, primary homonym of Microdon tuberculatus de Meijere, 1913), Paramixogaster brunettii nom. n. (= Mixogaster vespiformis Brunetti, 1913, secondary homonym of Microdon vespiformis de Meijere, 1908), Paramixogaster sacki nom. n. (= Myxogaster variegata Sack, 1922, secondary homonym of Ceratophya variegata Walker, 1852). An attempt is made to classify all available species names into (sub)genera and species groups. The resulting classification comprises 454 valid species and 98 synonyms (excluding misspellings), of which 17 valid names and three synonyms are left unplaced. The paper concludes with a discussion on diagnostic characters of Microdontinae.

Keywords

Key, revision, new genera, new species, new synonyms, new combinations, catalogue

Introduction

The Microdontinae (Diptera: Syrphidae) are found on all continents except Antarctica. The vast majority of more than 400 described species occurs in the tropics, of which almost half in the Neotropics. With little more than 50 species known from the Holarctic region, the group is relatively poorly represented in temperate regions. This partly explains why the taxonomy of the group has so far received little attention compared to other Syrphidae. This can also be explained by the morphological variation within the Microdontinae, which is arguably larger than in many families of Diptera Cyclorrhapha. Several authors have commented on the group’s paradoxical combination of a wealth of morphological diversity at the species level and a scarceness of group-defining characters (Bezzi 1915, Curran 1941, Shannon 1927). As a result, more than 300 out of approximately 400 valid species names are classified currently in the single genus Microdon Meigen, 1803. This apparent taxonomic indecisiveness seems to result not so much from a lack of morphological variation, but rather from an excess of it.

The classification of taxa, generic as well as specific, within the Microdontinae is the subject of the present paper. All available generic taxa of Microdontinae, as well as many species, are studied and compared in detail. Although phylogenetic relationships are still unclear for many taxa, we prefer to employ an ‘old-fashioned’ method of classification based on detailed comparative morphology over a ‘waste basket’ approach, despite their morphological differences (for more on this see Procedure under Material and Methods). A first phylogenetic analysis of the group is in press (Reemer and Ståhls in press), and in a number of instances the results of that study will be referred to.

Classification of Microdontinae within Syrphidae

When Meigen (1803) introduced the generic name Microdon, there was no intrafamilial classification of the family Syrphidae. The first family group name proposed for Microdon and its allies was Aphritadae Fleming, 1821 (spelled Aphritidae by Fleming 1822), separated from the ‘Syrphadae’ based on the absence of a facial tubercle. The Aphritidae also included Milesia Latreille, 1804 and related genera, which are nowadays included in the Eristalinae. Although the family group name Aphritidae has priority over Microdontinae, the latter name is maintained because Aphritidae has not been used after 1899, whereas Microdontinae has been used by many authors since (ICZN 1999: article 23.9, Sabrosky 1999).

Rondani (1845) first introduced the family group name Microdontinae (spelled as ‘Microdonellae’), based on the dentate scutellum of the type species Microdon mutabilis Linnaeus, 1758. Ever since, this group has been recognized as distinct from other Syrphidae, albeit under different spellings and taxonomic rankings. In early days (Lioy 1864, Brauer 1883, Williston 1886) and the single more recent case of Shatalkin (1975a, b), authors included genera which are nowadays considered to belong to other subfamilies. The placement of the group relative to other Syrphidae, however, has been far from stable. It would exceed the aim of the present paper to repeat here every author’s argumentations for their subsequent classifications over more than one and a half century. Table 1 lists the many different historical taxonomic treatments (spellings and classifications) the group has received.

Table 1.

Chronological overview of spellings, classifications and rankings of the family group names Aphritadae Fleming, 1821 and Microdonellae Rondani, 1845. All known references introducing a novel spelling or classification are included, as well as all known works that explicitly deal with the classification of the group. Works merely using previously suggested classifications are omitted.

Author Name / spelling Ranking and remarks
Fleming 1821: 55 Aphritadae Included Milesia Latreille and related genera.
Fleming 1822: 584 Aphritidae See Fleming 1821.
Rondani 1845: 451 Microdonellae One of eight ‘lineas’, equivalent to subfamilies.
Rondani 1856: 20, 54 Microdonina One of seven lineages, equivalent to subfamilies.
Rondani 1857: 206 Microdoninae See Rondani 1856.
Lioy 1864: 740 Microdon included in Psariti One of five subdivisions of Syrphidae, equivalent to subfamilies, including genera Chrysotoxum Meigen, 1803 and Psarus Latreille, 1804.
Nowicki 1873: 24 Microdontina One of eight subdivisions, equivalent to subfamlies.
Brauer 1883: 70 Microdinae Equivalent to tribe within subfamily (‘Gruppe’) Chrysotoxinae, including genera Chrysotoxum Meigen, 1803, Pipiza Meigen, Orthonevra Macquart, 1829 among other.
Williston 1886: xvi Microdonini Tribe within subfamily Syrphinae, including genera Chrysotoxum Meigen, 1803 and Psarus Latreille, 1804.
Verrall 1901: 658 Microdontinae One of seven subfamilies.
Shannon 1921: 67, 123; 1922: 35 Microdontinae One of ten subfamilies.
Sack 1928-1932: 234 Microdontinae One of 14 subfamilies.
Hull 1949: 305 Microdontinae One of 14 subfamilies, related to Eumerinae and Nausigasterinae. Spheginobaccha included.
Goffe 1952: 112 Microdontina Subtribe of tribe Volucellini, within subfamily Sphixinae (= Milesiinae of Wirth et al. 1965).
Wirth et al. 1965 Microdontini Tribe within subfamily Milesiinae
Thompson 1969: 75 Microdontinae Spheginobaccha excluded.
Thompson 1972: 85 Microdontidae Family.
Shatalkin 1975a, b Microdontinae Subfamily. Spheginobaccha included, as well as Alipumilio Shannon, 1927 and Nausigaster Williston, 1884.
Speight 1987: 172 Microdontidae Family.
Ståhls et al. 2003: 449 Microdontinae Subfamily. Spheginobaccha included. Alipumilio and Nausigaster excluded.
Cheng and Thompson 2008: 21 Microdontinae Subfamily.
Author Name / spelling Ranking and remarks
Fleming 1821: 55 Aphritadae Included Milesia Latreille and related genera.
Fleming 1822: 584 Aphritidae See Fleming 1821.
Rondani 1845: 451 Microdonellae One of eight ‘lineas’, equivalent to subfamilies.
Rondani 1856: 20, 54 Microdonina One of seven lineages, equivalent to subfamilies.
Rondani 1857: 206 Microdoninae See Rondani 1856.
Lioy 1864: 740 Microdon included in Psariti One of five subdivisions of Syrphidae, equivalent to subfamilies, including genera Chrysotoxum Meigen, 1803 and Psarus Latreille, 1804.
Nowicki 1873: 24 Microdontina One of eight subdivisions, equivalent to subfamlies.
Brauer 1883: 70 Microdinae Equivalent to tribe within subfamily (‘Gruppe’) Chrysotoxinae, including genera Chrysotoxum Meigen, 1803, Pipiza Meigen, Orthonevra Macquart, 1829 among other.
Williston 1886: xvi Microdonini Tribe within subfamily Syrphinae, including genera Chrysotoxum Meigen, 1803 and Psarus Latreille, 1804.
Verrall 1901: 658 Microdontinae One of seven subfamilies.
Shannon 1921: 67, 123; 1922: 35 Microdontinae One of ten subfamilies.
Sack 1928-1932: 234 Microdontinae One of 14 subfamilies.
Hull 1949: 305 Microdontinae One of 14 subfamilies, related to Eumerinae and Nausigasterinae. Spheginobaccha included.
Goffe 1952: 112 Microdontina Subtribe of tribe Volucellini, within subfamily Sphixinae (= Milesiinae of Wirth et al. 1965).
Wirth et al. 1965 Microdontini Tribe within subfamily Milesiinae
Thompson 1969: 75 Microdontinae Spheginobaccha excluded.
Thompson 1972: 85 Microdontidae Family.
Shatalkin 1975a, b Microdontinae Subfamily. Spheginobaccha included, as well as Alipumilio Shannon, 1927 and Nausigaster Williston, 1884.
Speight 1987: 172 Microdontidae Family.
Ståhls et al. 2003: 449 Microdontinae Subfamily. Spheginobaccha included. Alipumilio and Nausigaster excluded.
Cheng and Thompson 2008: 21 Microdontinae Subfamily.

The first to regard the Microdontinae as “presumably an old group early differentiated from the family” was Hull (1949). Goffe (1952) extensively reviewed the prior classifications of Syrphidae, including Microdontinae.

He placed the Microdontinae as a subtribe (‘Microdontina’) in the tribe Volucellini, together with the subtribe Volucellina, as part of the subfamily Sphixinae (more or less equivalent to the current Eristalinae). Thompson (1969) did not agree and treated the group again as basal within the Syrphidae. Then Thompson (1972) proposed to raise the group to family level. Shatalkin (1975a, b) did not follow this proposal, basing his argumentation only on the number of male pre-abdominal segments, but he agreed on the basal position of the group as a subfamily within the Syrphidae.

The proposal of Thompson (1972) to treat the Microdontinae as a separate family has not generally been followed. Speight (1987), however, based on his considerations of syrphid morphology, found Microdon to be aberrant from other Syrphidae to such an extent that he chose to follow Thompson’s proposal. In the study of Rotheray and Gilbert (1999), based on characters of immature stages, Microdontinae were placed as follows: (Eristalinae + (Microdontinae + (Syrphinae + Pipizini)). Subsequently, a number of studies recovered the Microdontinae as the sister-group of all other Syrphidae: Skevington and Yeates (2000) (based on molecular data), Ståhls et al. (2003) (based on molecular data combined with larval and adult morphology), and Rotheray and Gilbert (2008) (based on characters of the larval head). The results of Hippa and Ståhls (2005) (based on an extended set of adult morphological characters) differed from those previously mentioned by the placement of (Neoascia Williston, 1886 + Sphegina Meigen, 1822) as sister-group to all other Syrphidae. However, all of these authors treated the Microdontinae as a subfamily, as did Cheng and Thompson (2008). Speight (2010) has, however, continued to use familial rank. Reemer and Ståhls (in press), evaluating previous phylogenetic results as well as their newly generated evidence, see no scientific reason for changing the prevailing ranking of the Microdontinae and for that reason prefer nomenclatural stability.

Classifications and phylogenetic relationships within Microdontinae

There have been few previous attempts to generate a tribal classification of Microdontinae. Apart from the names Aphritidae Fleming and Microdontinae Rondani (see previous paragraph), only three family-group names have been proposed: Masarygidae Brèthes, 1908, Ceratophyini Hull, 1949 and Spheginobacchini Thompson, 1972. See Reemer and Ståhls (in press) for discussion on availability of these names. Application of the first two names is at present considered undesirable, as most phylogenetic relationships at suprageneric level are still too uncertain to recognize tribes, due to limited availability of taxa for molecular phylogenetic analysis and the obtained low support values for most of the resolved larger clades (Reemer and Ståhls in press). The tribe Spheginobacchini is the only of these names that continues to be recognized here, as we consider the sister group relationship of this taxon to the remaining Microdontinae well enough established (Ståhls et al. 2003, Reemer and Ståhls in press).

Cheng and Thompson (2008) gave an extensive overview of generic names of Microdontinae, which formed the starting point for the present paper. Since Meigen (1803) introduced the name Microdon, 59 genus-group names applicable to Microdontinae have been introduced (misspellings excluded) (Fig. 1). This number increased most rapidly during the first half of the 20th century. Since then, only nine new genus-group names have been proposed.

Figure 1.

Cumulative graph of introduced genus-group names of Microdontinae per decade (as percentage of total number of 59).

Figure 1.

Cumulative graph of introduced genus-group names of Microdontinae per decade (as percentage of total number of 59).

The number of previously introduced species-group names in Microdontinae is 514 (including synonyms and unvalid names). The cumulative graph of the number of species names per decade is similar to the one for genus-group names (Fig. 2). A majority of these species names (388) are currently classified into the genus Microdon. Most of the other (sub)genera contain only a few species. The very large genus Microdon thus constitutes one of the greatest taxonomic challenges of Syrphidae. The classification of so many species into one genus was a consequence of pragmaticism, as no comprehensive revisions were available.

Figure 2.

Cumulative graph of introduced species-group names of Microdontinae per decade (as percentage of total number of 514).

Figure 2.

Cumulative graph of introduced species-group names of Microdontinae per decade (as percentage of total number of 514).

Material and methods
Procedure

The phylogenetic results of Reemer and Ståhls (in press) are used as a first cue for the generic classification. When the evidence provided by these analyses is not conclusive or considered unconvincing (e.g. because of low support values), morphological characters are evaluated subjectively. Considerable weight is given to the structure of the male genitalia, but in all cases there are also external characters to support the groups. The species classification relies largely on this morphological evaluation.

Generally, a conservative approach is adopted towards changing the rank of taxa. Generic or subgeneric ranks as indicated by Cheng and Thompson (2008) are mostly maintained, unless these are contradicted by the results of the phylogenetic analyses of Reemer and Ståhls (in press). This is mainly relevant in the case of the genus Microdon. The species previously assigned to this genus were resolved as scattered over the phylogenetic trees of Reemer and Ståhls (in press). For some of these groups, genus group names are available, for some there are none. In several cases, genus group names that were previously treated as subgenera are now raised to generic level. In addition, new genus group names needed to be erected for several taxa that were previously included in Microdon. Given the uncertainties in the deeper branches of Microdontinae-phylogeny, these new group names could also have been given subgeneric rank within Microdon. However, this would suggest a close affinity with that genus, despite the fact that this is not indicated by the phylogenetic results. Moreover, we found it useful to split the genus Microdon into smaller natural groups which are more manageable than a genus containing more than 300 species. As this is only done for groups which have a high probability of being monophyletic (as indicated by phylogenetic results of Reemer and Ståhls (in press) or by subjective judgement of supposed synapomorphies), this procedure will facilitate further research on intergeneric phylogenetic relationships.

Acronyms of collections

The following acronyms are used to indicate entomological collections.

AMNH American Museum of Natural History, New York

AMS Australian Museum, Sydney

ANIC Australian National Insect Collection, Canberra

ANSP Academy of Natural Sciences of Pennsylvania, Philadelphia

BMNH British Museum of Natural History, London

CASB Chinese Acadamy of Science, Bejing

CM Carnegie Museum, Pittsburgh

CNC Canadian National Collection, Ottawa

CSCA California State Collection of Athropods, Sacramento

CSCS Central South University of Forestry and Technology, Changsha, Hunan

CU Cornell University, Ithaca

DEI Deutsches Entomologisches Institut, Müncheberg

DZUP Departamento de Zoologia da Universidade Federal do Paraná, Curitiba

HNHM Hungarian Natural History Museum, Budapest

INBIO Instituto Nacional de Biodiversidad, Heredia

MACN Museo Argentino de Ciencias Naturales, Buenos Aires

MCGD Museo Civico di Storia Naturale ‘G. Doria’, Genova

MCSN Museo Civico di Storia Naturale, Milan

MCZ Museum of Comparative Zoology, Harvard

MNHN Muséum National d’Histoire Naturelle, Paris

MRHNB Musée Royal d’Histoire Naturelle de Belgique, Brussels

MRSN Museu Regionale di Scienze Naturali, Turin

MZH Finnish Museum of Natural History, Helsinki

MZLU Museum of Zoology Lund University, Lund

MZM Museum of Zoology, University of Michigan, Ann Arbor

MZUN Museo Zoologico di Università degli Studi, Naples

MZUSP Museu de Zoologia da Universidade de São Paulo, São Paulo

NHRS Naturhistoriska Riksmuseet, Stockholm

NIAS Laboratory of Insect Systematics, National Institute of Agro-Environmental Sciences, Kannondai

NMB Naturhistorisches Museum Basel, Basel

NMSA Natal Museum, Pietermaritzburg

NMW Naturhistorisches Museum Wien, Vienna

NSMT National Science Museum Tokyo, Tokyo

NZCS National Zoological Collection of Surinam, Paramaribo

OHSU Ohio State University, Columbus

OUMNH Oxford University Museum of Natural History, Oxford

RBIN Institut Royal des Sciences Naturelles, Brussels

RMCA Musée Royal de l’Afrique Centrale, Tervuren

RMNH National Museum of Natural History NCB Naturalis, Leiden

QMBA Queensland Museum, Brisbane

QSBG Queen Sirikit Botanical Gardens, Chiang Mai (Thailand)

SAMA South Australian Museum, Adelaide

SAMC South African Museum, Cape Town

SEHU Systematic Entomology Hokkaido University, Sapporo

SEMC Snow Entomological Collections, University of Kansas, Lawrence

SMF Forschungsinstitut und Naturmuseum Senckenberg, Frankfurt

SMNS Staatliches Museum für Naturkunde, Stuttgart

SNSD Senckenberg Naturhistorische Sammlungen Dresden, Dresden

UFPR Universidade Federal dor Paraná, Curitiba

UMSP University of Minnesota, St. Paul

USNM United States National Museum, Smithsonian Institution, Washington D.C.

UTOR Instituto e Museo di Zoologia di Torino, Turin

WSU Washington State University, Pullman

ZFMK Zoologisches Forschungsinstitut und Museum Alexander Koenig, Bonn

ZISP Russian Academy of Sciences, Zoological Institute, St. Petersburg

ZMAN Zoological Museum of Amsterdam - now housed in RMNH, Leiden

ZMHU Zoologisches Museum der Humboldt Universität, Berlin

ZMUC Zoological Museum University of Copenhagen, Copenhagen

ZSI Zoological Survey of India, Calcutta

ZSM Zoologische Staatssammlung, Munich


A few private collections have also been studied. These are referred to in text and appendices by giving the initials and full surname of the owner.

If specimens referred to in the species descriptions in Appendix 1 were used for DNA extraction, this is mentioned by citing the voucher codes on the specimen label (e.g. “DNA voucher G. Ståhls Y0909”). These codes are used by the molecular lab of the Finnish Museum of Natural History (MZH), Helsinki.

Dissection and microscopy

Male genitalia were dissected and macerated in an aqueous 10% KOH solution at ambient temperature for 12–24 hours, rinsed in water and stored in glycerol. Drawings of male genitalia were made with the aid of a drawing tube attached to a Wild M20 compound microscope. Photographs of (parts of) specimens were taken through an Olympus SZX12 motorized stereozoom microscope, using Analysis Extended Focal Imaging Software.

Morphology

Most of the morphological terminology used in this paper is derived from McAlpine (1981), as specifically applied to Syrphidae by Thompson (1999), who also introduced some new terms. Cheng and Thompson (2008) introduced a few more with special relevance to Microdontinae. For some characters used in the present paper, these works do not provide applicable terms. In these cases terminology is based on Hippa and Ståhls (2005) (e.g. antennal fossa, antetergite) and Speight (1987) (e.g. anterolateral callus of tergite 1, anterior sclerite of sternite 2). For the terminology of the male genitalia McAlpine (1981) was used, supplemented with some more recent considerations as summarized by Sinclair (2000) and adopted by Cumming and Wood (2009). This terminology is worked out for Microdontinae in detail in Reemer and Ståhls (in press).

Key to genera and species groups

Two keys to genera and generic groups of Microdontinae have been published previously: Hull (1949) and Cheng and Thompson (2008). Characters used in those keys have been considered and some are also used here, but many new characters were necessary to accomodate for new genera and redefined genera. Several taxa are keyed out more than once, either because they are borderline cases or because the key characters are variable between species within these groups. In a few cases the key leads to a species, when this species is an exception among its congeners with regard to the key characters.

A discussion of diagnostic characters of Microdontinae can be found in the Discussion paragraph. A key to distinguish this subfamily from other Syrphidae is also presented there.

1 Postmetacoxal bridge incomplete (metapleura separated from each other) 97
Postmetacoxal bridge complete (metapleura connected posteriad of metacoxa, often only narrowly) 2
2 Vein R4+5 without posterior appendix extending into cell r4+5 (Figs 3, 28, 404) 74
Vein R4+5 with posterior appendix extending into cell r4+5 (Figs 14, 17, 206) 3
3 Postpronotum bare 67
Postpronotum pilose 4
4 Abdomen constricted 58
Abdomen not constricted (oval, parallel-sided or tapering) 5
5 Anepisternum with bare part limited to ventral half of the anepisternum, or entirely pilose 43
Anepisternum extensively bare, with bare part reaching dorsad to above half the height of the anepisternum 6
6 Propleuron (proepimeron) bare 13
Propleuron (proepimeron) pilose 7
7 Postero-apical corner of wing cell r4+5 more or less rectangular or acute, always with small appendix (e.g. Figs 14, 17, 28, 55) 11
Postero-apical corner of wing cell r4+5 widely rounded, sometimes with small appendix (e.g. Figs 177, 206, 210, 289) 8
8 Katepimeron more or less flat (may be a little elevated or with an ill-developed carina, but not convex), sometimes with rows of microtrichia. Abdomen narrow, clearly less than 1.5 times as wide as thorax (Fig. 294) Peradon: flavofasium-group (in part)
Katepimeron convex, never with microtrichia. Abdomen wide, about 1.5 times as wide as thorax (Figs 176, 197, 200) 9
9 Apical crossvein M1 with outward angle, usually with a small outward appendix, anteriorly recurrent (Fig. 177) Microdon (Chymophila)
Apical crossvein M1 without outward angle (Fig. 206, 210) 10
10 Lateral oral margins not or only slightly produced: anterolateral corners not angular (Fig. 202, 207) Microdon s.s.
Lateral oral margins strongly produced: anterolateral corners angular (Fig. 229). Microdon s.s.: virgo-group
11 Tergites 3 and 4 not fused, able to articulate independently (Fig. 44) Ceratophya (in part)
Tergites 3 and 4 fused, not able to articulate independently, although a suture between the tergites is usually visible (look at lateral margins for best judgement) 12
12 Eye bare. Male genitalia: phallus apically furcate (Figs 369, 371, 376) Serichlamys
Eye pilose. Male genitalia: phallus unfurcate (Fig. 135) Laetodon
13 Sternites 2 and 3 (often also 1 and 2) separated by unusually wide membraneous part, about as wide as sternite 2 medially or wider (Fig. 393, 394). Antetergite enlarged, longer than tergite 1 medially, almost at level with tergite 1 Stipomorpha
Sternites 2 and 3 not separated by unusually wide membraneous part. Antetergite small, shorter than or as long as tergite 1 medially, often not at level with tergite 1 but making a smaller angle 14
14 Postero-apical corner of wing cell r4+5 more or less rectangular or acute (usually with small appendix) (Figs 14, 17, 28, 55) 29
Postero-apical corner of wing cell r4+5 widely rounded (sometimes with small appendix) (Figs 177, 206, 210, 289) 15
15 Basoflagellomere shorter than scape (Fig. 229) 24
Basoflagellomere as long as or longer than scape (Fig. 293) 16
16 Sternite 1 pilose (sometimes only short and sparsely) 21
Sternite 1 bare 17
17 Entire body with metallic green to bluish colouration, densely punctate. Mimics of chrysidid wasps (Hymenoptera: Chrysididae) (Figs 63–67) Chrysidimyia
At most thorax with faint metallic hues 18
18 Abdomen constricted basally (Fig. 295) Peradon: trivittatum-group (in part)
Abdomen not constricted 19
19 Male with bifurcate basoflagellomere (Fig. 61). Female unknown, possibly with curved or sickle-shaped basoflagellomere. Australian taxon Cervicorniphora
Basoflagellomere unfurcate; oval or parallel-sided. Neotropical taxa 20
20 Tergites without fasciae or vittae of golden or silver pile. Basoflagellomere less than twice as long as scape Peradon: bidens-group
Tergites usually with fasciae and/or vittae of golden or silver pile. If not, then basoflagellomere more than twice as long as scape Peradon: flavofascium-group (in part)
21 Tergite 2 with tubercle halfway on lateral margin (Fig. 421) Ubristes
Tergite 2 without tubercle on lateral margin 22
22 Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere less than twice as long as wide Microdon rieki (Australia)
Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere at least four times as long as wide 23
23 Brownish species with long, bee-like pilosity. Scutellum without calcars Microdon (Myiacerapis)
Metallic green, sparsely pilose species, reminiscent of chrysidid wasp. Scutellum with calcars Microdon s.s. (in part: macquartii)
24 Wings hyaline, at most subtly infuscated 26
Wings with black and yellow colour pattern 25
25 Abdomen without conspicuous fasciae of long pile. Scutellum without calcars. < 20 mm Microdon s.l.: mirabilis-group
Abdomen with conspicuous fasciae of long, white pile; apex long, orange pilose. Scutellum with large calcars. >20 mm. Mimics of Eulaema (Hymenoptera: Euglossidae) Syrphipogon
26 Vertex convex and shining Pseudomicrodon (in part: biluminiferus)
Vertex more or less flat, dull 27
27 Tergites 3 and 4 about equally wide, with lateral margins parallel Microdon waterhousei Ferguson
Tergites 3 wider than tergite 4, with lateral margins converging posteriad 28
28 Lateral oral margins strongly produced: anterolateral corners angular (Fig. 229) Microdon s.s.: virgo-group (in part)
Lateral oral margins not or only slightly produced: anterolateral corners not angular (Figs 202, 207) Microdon s.l.: erythros-group
29 Antenna shorter than distance between antennal fossa and anterior oral margin 40
Antenna as long as or longer than distance between antennal fossa and anterior oral margin 30
30 Scutellum with apical calcars 34
Scutellum without apical calcars, but sometimes sulcate apicomedially or with small patches of microtrichia where calcars could be expected 31
31 Tergites 3 and 4 not fused, able to articulate independently 33
Tergites 3 and 4 fused, not able to articulate independently, although a suture between the tergites is usually visible 32
32 Sternite 1 bare Menidon falcatus (in part)
Sternite 1 pilose Microdon (Dimeraspis) adventitus
[The Australian Archimicrodon browni (Thompson) keys here too, but condition of pilosity of sternite 1 unknown.]
33 Male basoflagellomere without long pile. Both sexes: hind tibia in lateral view at least 1.5 times as wide as hind metatarsus Ceratophya (in part), South America
Male basoflagellomere with long pile. Both sexes: hind tibia in lateral view about as wide as hind metatarsus Kryptopyga (in part), Southeast Asia
34 Occiput dorsally widened (even if only slightly): dorsal eye margin diverging from hind margin of head (Figs 5, 86, 229) 36
Occiput evenly narrow over entire length: dorsal eye margin parallel to hind margin of head (Fig. 191). 35
35 Male: first tarsomere of hind leg dorsally without longitudinal groove; strongly swollen: about twice as wide as apex of hind tibia Microdon (s.l.) tarsalis
Male: first tarsomere of hind leg dorsally with wide longitudinal groove; at most 1.5 times as wide as apex of hind tibia Megodon
36 Scutellar calcars large and blunt (Fig. 183). Male: first tarsomere of hind leg about twice as wide as apex of hind tibia Microdon (Dimeraspis) globosus
Scutellar calcars either absent, very small or well-developed and pointed apically. Male: first tarsomere of hind leg at most 1.5 times as wide as apex of hind tibia 37
37 Vertex convex and shining, bare or sparsely pilose only on posterior half (Figs 70, 71) Domodon
Vertex not convex and shining, entirely pilose 38
38 Basoflagellomere oval (Figs 365, 367, 370) Serichlamys
Basoflagellomere sickle-shaped (Fig. 154) 39
39 Abdomen largely or entirely yellow (Fig. 151)Menidon falcatus (in part)
Abdomen black Archimicrodon (in part: one undescribed African species)
40 Anepimeron bare on ventral half. Male with eye margins parallel at level of frons, not approaching Mermerizon
Anepimeron entirely pilose. Male with eye margins approaching each other at level of frons. 41
41 Scutellum with large, apically rounded and flattened calcars. Archimicrodon (Hovamicrodon)
Scutellum without calcars or with calcars pointed apically 42
42 Male genitalia: surstylus in lateral view without long posterior process (Figs 9, 15) Archimicrodon s.s.
Male genitalia: surstylus in lateral view with long posterior process (Figs 19, 22–26) Archimicrodon s.l.
43 Basoflagellomere more or less oval or parallel-sided, sometimes with acute apex (Figs 66, 255, 325). 45
Basoflagellomere sickle-shaped or flag-shaped (Figs 252, 425) 44
44 Basoflagellomere sickle-shaped: thickened basally, curved dorsad apically. Arista bare. Eye reduced, so gena, vertex and occiput wide (Fig. 252) Oligeriops
Basoflagellomere flag-shaped: strongly widened and laterally flattened (Fig. 425). Arista pilose (pile at least half as long as width of arista). Eyes of normal size Undescribed genus #1, species AUS-01
45 Basoflagellomere shorter than scape 54
Basoflagellomere as long as or longer than scape 46
46 Antenna as long as or longer than distance between antennal fossa and anterior oral margin 49
Antenna shorter than distance between antennal fossa and anterior oral margin 47
47 Tergite 2 with pair of depressed areas (as in Fig. 287); lateral margins of tergite 2 subcircular, widest point clearly before posterior margin Omegasyrphus
Tergite 2 without depressed areas; widest point of tergite 2 at posterior margin. 48
48 Wing with conspicuous black markings in apical half (Fig. 230) Microdon pictipennis
Wing without conspicuous black markings, only vaguely infuscated along crossveins Microdon nigromarginalis
49 Tergites 3 and 4 fused, not able to articulate independently, although a suture between the tergites is usually visible (look at lateral margins for best judgement) 51
Tergites 3 and 4 not fused, able to articulate independently (Fig. 44) 50
50 Dorsal half of occiput slightly widened: maximum width in lateral view less than 1/4 of eye width. Tergite 4 in lateral view approximately perpendicular to tergite 2 (Fig. 43, 44) Ceratophya
Dorsal half of occiput strongly widened: maximum width in lateral view about 1/2 of eye width. Tergite 4 in lateral view not perpendicular to tergite 2 Microdon shirakii
51 Metallic green species, mimics of chrysidid wasps (Fig. 63, 64) Chrysidimyia
Brownish or partly orange species 52
52 Basoflagellomere more than three times as long as scape; with long pilosity in male (Fig. 325) Ptilobactrum
Basoflagellomere less than three times as long as scape; bare in male 53
53 Abdomen narrow: more than 1.5 times as long as wide (Figs 163, 167) Metadon
Abdomen wide: less than 1.5 times as long as wide (Fig. 181) Microdon (Dimeraspis)
54 Abdomen about as long as wide Microdon (Dimeraspis) abditus
Abdomen clearly longer than wide 55
55 Metallic green or blue flies, mimics of chrysidid wasps (Fig. 63, 64) Chrysidimyia
Not metallic green or blue flies 56
56 Tergite 1 long, with hind margin very rounded; length : width ratio 1:2 or longer (Fig. 81, 83) Heliodon
Tergite 1 shorter, with hind margin less rounded; length : width ratio 1:2.5 or shorter 57
57 Tergite 2 with pair of depressed areas (Fig. 287). Abdomen more than 2.5 times as long as wide (Fig. 285). Alula bare Parocyptamus
Tergite 2 without depressed areas. Abdomen less than 2.5 times as long as wide (Fig. 163, 167). Alula microtrichose along margins Metadon
58 Transverse suture incomplete: not visible medially on mesoscutum 61
Transverse suture complete: extending from one notopleuron to the other 59
59 Katepimeron pilose. Male basoflagellomere with long pile (Fig. 47, 54) Ceratrichomyia
Katepimeron bare. Male basoflagellomere without long pile 60
60 Frons laterally without concave area; without sharply defined ridge from lunula to eye margin Indascia (in part)
Frons laterally with concave area, covered with dense golden pilosity; ventrally this area is delimited by a sharply defined ridge, which runs from the lunula to the eye margin (Figs 410, 413, 414) Thompsodon conspicillifrons
61 Tergites 3 and 4 not fused, able to articulate independently (Fig. 120). Male: sternite 4 not visible in ventral view: completely covered by sternite 3 and lateral margins of tergites (Fig. 123). Male basoflagellomere with long pile (Fig. 122) Kryptopyga pendulosa
Tergites 3 and 4 fused, not able to articulate idependently (although a suture between these tergites is usually visible) 62
62 Basoflagellomere longer than scape 64
Basoflagellomere shorter than or as long as scape 63
63 Tergite 2 at most as long as anterior width (Fig. 81) Heliodon
Tergite 2 more than twice as long as anterior width (Fig. 347) Rhopalosyrphus (s.l.) oreokawensis
64 Vertex convex, shining, sparsely pilose to bare (Fig. 310, 315) Pseudomicrodon
Vertex more or less flat, dull and entirely pilose (Fig. 339, 344) 65
65 Tergite 2 with anterior margin about as wide as posterior margin (Fig. 295) Peradon: trivittatum-group
Tergite 2 with anterior margin at least 1.5 times as wide as posterior margin (Fig. 332, 337, 342) 66
66 Katepimeron pilose (sometimes only along anterior margin) Rhopalosyrphus s.s.
Katepimeron bare Rhopalosyrphus s.l.
67 Abdomen oval or elongate, not constricted in dorsal view (Fig. 35, 269, 293, 294) 69
Abdomen constricted in dorsal view (i.e. with narrowest point (in dorsal view) at tergite 2 and widest point at tergite 3 or 4) (Fig. 271, 272, 276) 68
68 Postero-apical corner of wing cell r4+5 widely rounded. Segment 2 longer than thorax (Fig. 59) Ceriomicrodon petiolatus
Postero-apical corner of wing cell r4+5 more or less rectangular or acute, with small appendix (Fig. 271). Segment 2 usually shorter than or as long as thorax (Figs 269, 284) (except in one undescribed African taxon) Paramixogaster (in part)
69 Basoflagellomere about six times as long as scape (Fig. 36) Bardistopus
Basoflagellomere at most four times as long as scape 70
70 Abdomen about as long as wide, with tergite 2 about as long as tergites 3 and 4 together (Fig. 397, 398) Sulcodon
Abdomen at least 1.5 times as long as wide, with tergite 2 less than half as long as tergites 3 and 4 together 71
71 Face medially with vitta of transversely wrinkled texture (Fig. 291) Peradon: flavofascium-group (in part)
Face medially smooth 72
72 Basoflagellomere longer than scape Paramixogaster (in part: Paramixogaster acantholepidis, Paramixogaster crematogastri)
Basoflagellomere shorter than scape 73
73 Tergite 2 twice as wide as long or wider; entirely black Metadon (in part: Metadon bifasciatus)
Tergite 2 about 1.5 times as wide as long; with large yellow marking in shape of an inverted “V” Microdon trigonospilus Bezzi
74 Vein M anteriorly without small stump extending into cell r4+5 (Fig. 3, 389, 404) 76
Vein M anteriorly with small stump extending into cell r4+5 (Fig. 28, 242, 244) 75
75 Crossvein r-m located between basal 1/4 and 1/3 of cell dm (Fig. 242, 244) Mixogaster
Crossvein r-m located within basal 1/7 of cell dm (Fig. 28) Aristosyrphus (in part: some specimens of Aristosyrphus primus)
76 Face with median tubercle on dorsal half (Fig. 31) Aristosyrphus (Eurypterosyrphus)
Face without median tubercle (Fig. 5) 77
77 Vein M1 more or less straight, not parallel to wing margin, making straight angle with vein R4+5 (Fig. 14, 166, 219) 79
Vein M1 at least in anterior half (sometimes also in posterior half) oblique, more or less parallel to wing margin, making acute angle with vein R4+5 (Fig. 3, 28) 78
78 Abdomen constricted or parallel-sided, not or only slightly wider than thorax (Fig. 27) Aristosyrphus s.s.
Abdomen oval, clearly wider than thorax (cf. Fig. 7, 20) Afromicrodon
79 Abdomen constricted (i.e. with narrowest point at tergite 2 and widest point at tergite 3 or 4) or elongate and parallel-sided (Figs 103, 262, 284) 89
Abdomen oval (Figs 7, 10, 20, 401) or tapering / triangular (Figs 388, 392) (tergite 2 may be quite narrow anteriorly, but then the abdomen does not get wider beyond posterior margin of tergite 2) 80
80 Sternites 2 and 3 (often also 1 and 2) separated by unusually wide membraneous part, about as wide as sternite 2 medially or wider (Figs 393, 394). Antetergite of tergite 1 enlarged, longer than tergite 1 medially, almost at level with tergite 1 Stipomorpha
Sternites 2 and 3 not separated by unusually wide membraneous part. Antetergite small, shorter than or as long as tergite 1 medially, often not at level with tergite 1 but making a smaller angle 81
81 Basoflagellomere shorter than or as long as scape (basoflagellomere never furcate) 93
Basoflagellomere longer than scape (basoflagellomere sometimes furcate in male) 82
82 Antenna at least as long as distance between antennal fossa and anterior oral margin, furcate in male (Figs 39, 77, 138, 144, 356–361) 86
Antenna shorter than distance between antennal fossa and anterior oral margin, never furcate 83
83 Thorax and abdomen black Archimicrodon s.l. (undescribed taxa from Papua New Guinea)
Thorax and abdomen yellow and black 84
84 Postpronotum bare Surimyia
Postpronotum pilose 85
85 Position of crossvein r-m at same level as bm-cu (Fig. 258) Paragodon
Position of crossvein r-m more apical: approximately at basal 1/8 of cell dm Hypselosyrphus (in part)
86 Scutellum sulcate apicomedially (cf. Fig. 183) 88
Scutellum not sulcate apicomedially, more or less semicircular 87
87 Antenna inserted dorsally on head: at or above dorsal eye margin. Male basoflagellomere multifurcate (Figs 138, 142–144, 149) Masarygus
Antenna inserted below dorsal eye margin. Male basoflagellomere bifurcate (Figs 356–360) Schizoceratomyia
88 Katepisternum pilose. Metasternum developed and pilose Furcantenna
Katepisternum bare. Metasternum underdeveloped and bare Carreramyia
89 Postpronotum pilose 91
Postpronotum bare 90
90 Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere more than 3 times as long as wide (Figs 269–277) Paramixogaster (in part: Paramixogaster decipiens (de Meijere) and undescribed Australian sp.)
Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere less than 2 times as long as wide (Figs 301, 302, 306) Piruwa
91 Mesoscutum with transverse suture complete (reaching from one notopleuron to the other) Indascia
Mesoscutum with transverse suture not complete (not visible medially) 92
92 Antenna longer than distance between antennal fossa and anterior oral margin. Male basoflagellomere bifurcate (Figs 430, 432) Undescribed genus #2, species MCR-02
Antenna shorter than distance between antennal fossa and anterior oral margin. Male basoflagellomere not furcate (Figs 262–266) Paramicrodon
93 Katepimeron pilose Hypselosyrphus ulopodus
Katepimeron bare 94
94 Occiput wide, both dorsally and ventrally (Fig. 328) Rhoga
Occiput narrow, at least on ventral half (Figs 5, 229, 403) 95
95 Postpronotum bare Surimyia
Postpronotum pilose 96
96 Vertex not produced, more or less flat (Figs 3–5) Afromicrodon
Vertex produced, more or less convex (Figs 99, 100) Hypselosyrphus
97 Abdomen oval or more or less parallel-sided, not constricted (Fig. 330). Occiput without creases (Fig. 328) Rhoga (in part: maculata, mellea, sepulchrasilva)
Abdomen elongate and constricted (narrowest point at transition between tergites 2 and 3) (Figs 377, 382). Occiput with distinct creases (Figs 379, 384) 98
98 Proanepisternum without row of long stiff pile. Eye bare Spheginobaccha (perialla-group)
Proanepisternum with row of long stiff pile. Eye bare or pilose 99
99 Eye pilose. Alula microtrichose Spheginobaccha (macropoda-group)
Eye bare. Alula partially bare Spheginobaccha (rotundiceps-group)
1 Postmetacoxal bridge incomplete (metapleura separated from each other) 97
Postmetacoxal bridge complete (metapleura connected posteriad of metacoxa, often only narrowly) 2
2 Vein R4+5 without posterior appendix extending into cell r4+5 (Figs 3, 28, 404) 74
Vein R4+5 with posterior appendix extending into cell r4+5 (Figs 14, 17, 206) 3
3 Postpronotum bare 67
Postpronotum pilose 4
4 Abdomen constricted 58
Abdomen not constricted (oval, parallel-sided or tapering) 5
5 Anepisternum with bare part limited to ventral half of the anepisternum, or entirely pilose 43
Anepisternum extensively bare, with bare part reaching dorsad to above half the height of the anepisternum 6
6 Propleuron (proepimeron) bare 13
Propleuron (proepimeron) pilose 7
7 Postero-apical corner of wing cell r4+5 more or less rectangular or acute, always with small appendix (e.g. Figs 14, 17, 28, 55) 11
Postero-apical corner of wing cell r4+5 widely rounded, sometimes with small appendix (e.g. Figs 177, 206, 210, 289) 8
8 Katepimeron more or less flat (may be a little elevated or with an ill-developed carina, but not convex), sometimes with rows of microtrichia. Abdomen narrow, clearly less than 1.5 times as wide as thorax (Fig. 294) Peradon: flavofasium-group (in part)
Katepimeron convex, never with microtrichia. Abdomen wide, about 1.5 times as wide as thorax (Figs 176, 197, 200) 9
9 Apical crossvein M1 with outward angle, usually with a small outward appendix, anteriorly recurrent (Fig. 177) Microdon (Chymophila)
Apical crossvein M1 without outward angle (Fig. 206, 210) 10
10 Lateral oral margins not or only slightly produced: anterolateral corners not angular (Fig. 202, 207) Microdon s.s.
Lateral oral margins strongly produced: anterolateral corners angular (Fig. 229). Microdon s.s.: virgo-group
11 Tergites 3 and 4 not fused, able to articulate independently (Fig. 44) Ceratophya (in part)
Tergites 3 and 4 fused, not able to articulate independently, although a suture between the tergites is usually visible (look at lateral margins for best judgement) 12
12 Eye bare. Male genitalia: phallus apically furcate (Figs 369, 371, 376) Serichlamys
Eye pilose. Male genitalia: phallus unfurcate (Fig. 135) Laetodon
13 Sternites 2 and 3 (often also 1 and 2) separated by unusually wide membraneous part, about as wide as sternite 2 medially or wider (Fig. 393, 394). Antetergite enlarged, longer than tergite 1 medially, almost at level with tergite 1 Stipomorpha
Sternites 2 and 3 not separated by unusually wide membraneous part. Antetergite small, shorter than or as long as tergite 1 medially, often not at level with tergite 1 but making a smaller angle 14
14 Postero-apical corner of wing cell r4+5 more or less rectangular or acute (usually with small appendix) (Figs 14, 17, 28, 55) 29
Postero-apical corner of wing cell r4+5 widely rounded (sometimes with small appendix) (Figs 177, 206, 210, 289) 15
15 Basoflagellomere shorter than scape (Fig. 229) 24
Basoflagellomere as long as or longer than scape (Fig. 293) 16
16 Sternite 1 pilose (sometimes only short and sparsely) 21
Sternite 1 bare 17
17 Entire body with metallic green to bluish colouration, densely punctate. Mimics of chrysidid wasps (Hymenoptera: Chrysididae) (Figs 63–67) Chrysidimyia
At most thorax with faint metallic hues 18
18 Abdomen constricted basally (Fig. 295) Peradon: trivittatum-group (in part)
Abdomen not constricted 19
19 Male with bifurcate basoflagellomere (Fig. 61). Female unknown, possibly with curved or sickle-shaped basoflagellomere. Australian taxon Cervicorniphora
Basoflagellomere unfurcate; oval or parallel-sided. Neotropical taxa 20
20 Tergites without fasciae or vittae of golden or silver pile. Basoflagellomere less than twice as long as scape Peradon: bidens-group
Tergites usually with fasciae and/or vittae of golden or silver pile. If not, then basoflagellomere more than twice as long as scape Peradon: flavofascium-group (in part)
21 Tergite 2 with tubercle halfway on lateral margin (Fig. 421) Ubristes
Tergite 2 without tubercle on lateral margin 22
22 Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere less than twice as long as wide Microdon rieki (Australia)
Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere at least four times as long as wide 23
23 Brownish species with long, bee-like pilosity. Scutellum without calcars Microdon (Myiacerapis)
Metallic green, sparsely pilose species, reminiscent of chrysidid wasp. Scutellum with calcars Microdon s.s. (in part: macquartii)
24 Wings hyaline, at most subtly infuscated 26
Wings with black and yellow colour pattern 25
25 Abdomen without conspicuous fasciae of long pile. Scutellum without calcars. < 20 mm Microdon s.l.: mirabilis-group
Abdomen with conspicuous fasciae of long, white pile; apex long, orange pilose. Scutellum with large calcars. >20 mm. Mimics of Eulaema (Hymenoptera: Euglossidae) Syrphipogon
26 Vertex convex and shining Pseudomicrodon (in part: biluminiferus)
Vertex more or less flat, dull 27
27 Tergites 3 and 4 about equally wide, with lateral margins parallel Microdon waterhousei Ferguson
Tergites 3 wider than tergite 4, with lateral margins converging posteriad 28
28 Lateral oral margins strongly produced: anterolateral corners angular (Fig. 229) Microdon s.s.: virgo-group (in part)
Lateral oral margins not or only slightly produced: anterolateral corners not angular (Figs 202, 207) Microdon s.l.: erythros-group
29 Antenna shorter than distance between antennal fossa and anterior oral margin 40
Antenna as long as or longer than distance between antennal fossa and anterior oral margin 30
30 Scutellum with apical calcars 34
Scutellum without apical calcars, but sometimes sulcate apicomedially or with small patches of microtrichia where calcars could be expected 31
31 Tergites 3 and 4 not fused, able to articulate independently 33
Tergites 3 and 4 fused, not able to articulate independently, although a suture between the tergites is usually visible 32
32 Sternite 1 bare Menidon falcatus (in part)
Sternite 1 pilose Microdon (Dimeraspis) adventitus
[The Australian Archimicrodon browni (Thompson) keys here too, but condition of pilosity of sternite 1 unknown.]
33 Male basoflagellomere without long pile. Both sexes: hind tibia in lateral view at least 1.5 times as wide as hind metatarsus Ceratophya (in part), South America
Male basoflagellomere with long pile. Both sexes: hind tibia in lateral view about as wide as hind metatarsus Kryptopyga (in part), Southeast Asia
34 Occiput dorsally widened (even if only slightly): dorsal eye margin diverging from hind margin of head (Figs 5, 86, 229) 36
Occiput evenly narrow over entire length: dorsal eye margin parallel to hind margin of head (Fig. 191). 35
35 Male: first tarsomere of hind leg dorsally without longitudinal groove; strongly swollen: about twice as wide as apex of hind tibia Microdon (s.l.) tarsalis
Male: first tarsomere of hind leg dorsally with wide longitudinal groove; at most 1.5 times as wide as apex of hind tibia Megodon
36 Scutellar calcars large and blunt (Fig. 183). Male: first tarsomere of hind leg about twice as wide as apex of hind tibia Microdon (Dimeraspis) globosus
Scutellar calcars either absent, very small or well-developed and pointed apically. Male: first tarsomere of hind leg at most 1.5 times as wide as apex of hind tibia 37
37 Vertex convex and shining, bare or sparsely pilose only on posterior half (Figs 70, 71) Domodon
Vertex not convex and shining, entirely pilose 38
38 Basoflagellomere oval (Figs 365, 367, 370) Serichlamys
Basoflagellomere sickle-shaped (Fig. 154) 39
39 Abdomen largely or entirely yellow (Fig. 151)Menidon falcatus (in part)
Abdomen black Archimicrodon (in part: one undescribed African species)
40 Anepimeron bare on ventral half. Male with eye margins parallel at level of frons, not approaching Mermerizon
Anepimeron entirely pilose. Male with eye margins approaching each other at level of frons. 41
41 Scutellum with large, apically rounded and flattened calcars. Archimicrodon (Hovamicrodon)
Scutellum without calcars or with calcars pointed apically 42
42 Male genitalia: surstylus in lateral view without long posterior process (Figs 9, 15) Archimicrodon s.s.
Male genitalia: surstylus in lateral view with long posterior process (Figs 19, 22–26) Archimicrodon s.l.
43 Basoflagellomere more or less oval or parallel-sided, sometimes with acute apex (Figs 66, 255, 325). 45
Basoflagellomere sickle-shaped or flag-shaped (Figs 252, 425) 44
44 Basoflagellomere sickle-shaped: thickened basally, curved dorsad apically. Arista bare. Eye reduced, so gena, vertex and occiput wide (Fig. 252) Oligeriops
Basoflagellomere flag-shaped: strongly widened and laterally flattened (Fig. 425). Arista pilose (pile at least half as long as width of arista). Eyes of normal size Undescribed genus #1, species AUS-01
45 Basoflagellomere shorter than scape 54
Basoflagellomere as long as or longer than scape 46
46 Antenna as long as or longer than distance between antennal fossa and anterior oral margin 49
Antenna shorter than distance between antennal fossa and anterior oral margin 47
47 Tergite 2 with pair of depressed areas (as in Fig. 287); lateral margins of tergite 2 subcircular, widest point clearly before posterior margin Omegasyrphus
Tergite 2 without depressed areas; widest point of tergite 2 at posterior margin. 48
48 Wing with conspicuous black markings in apical half (Fig. 230) Microdon pictipennis
Wing without conspicuous black markings, only vaguely infuscated along crossveins Microdon nigromarginalis
49 Tergites 3 and 4 fused, not able to articulate independently, although a suture between the tergites is usually visible (look at lateral margins for best judgement) 51
Tergites 3 and 4 not fused, able to articulate independently (Fig. 44) 50
50 Dorsal half of occiput slightly widened: maximum width in lateral view less than 1/4 of eye width. Tergite 4 in lateral view approximately perpendicular to tergite 2 (Fig. 43, 44) Ceratophya
Dorsal half of occiput strongly widened: maximum width in lateral view about 1/2 of eye width. Tergite 4 in lateral view not perpendicular to tergite 2 Microdon shirakii
51 Metallic green species, mimics of chrysidid wasps (Fig. 63, 64) Chrysidimyia
Brownish or partly orange species 52
52 Basoflagellomere more than three times as long as scape; with long pilosity in male (Fig. 325) Ptilobactrum
Basoflagellomere less than three times as long as scape; bare in male 53
53 Abdomen narrow: more than 1.5 times as long as wide (Figs 163, 167) Metadon
Abdomen wide: less than 1.5 times as long as wide (Fig. 181) Microdon (Dimeraspis)
54 Abdomen about as long as wide Microdon (Dimeraspis) abditus
Abdomen clearly longer than wide 55
55 Metallic green or blue flies, mimics of chrysidid wasps (Fig. 63, 64) Chrysidimyia
Not metallic green or blue flies 56
56 Tergite 1 long, with hind margin very rounded; length : width ratio 1:2 or longer (Fig. 81, 83) Heliodon
Tergite 1 shorter, with hind margin less rounded; length : width ratio 1:2.5 or shorter 57
57 Tergite 2 with pair of depressed areas (Fig. 287). Abdomen more than 2.5 times as long as wide (Fig. 285). Alula bare Parocyptamus
Tergite 2 without depressed areas. Abdomen less than 2.5 times as long as wide (Fig. 163, 167). Alula microtrichose along margins Metadon
58 Transverse suture incomplete: not visible medially on mesoscutum 61
Transverse suture complete: extending from one notopleuron to the other 59
59 Katepimeron pilose. Male basoflagellomere with long pile (Fig. 47, 54) Ceratrichomyia
Katepimeron bare. Male basoflagellomere without long pile 60
60 Frons laterally without concave area; without sharply defined ridge from lunula to eye margin Indascia (in part)
Frons laterally with concave area, covered with dense golden pilosity; ventrally this area is delimited by a sharply defined ridge, which runs from the lunula to the eye margin (Figs 410, 413, 414) Thompsodon conspicillifrons
61 Tergites 3 and 4 not fused, able to articulate independently (Fig. 120). Male: sternite 4 not visible in ventral view: completely covered by sternite 3 and lateral margins of tergites (Fig. 123). Male basoflagellomere with long pile (Fig. 122) Kryptopyga pendulosa
Tergites 3 and 4 fused, not able to articulate idependently (although a suture between these tergites is usually visible) 62
62 Basoflagellomere longer than scape 64
Basoflagellomere shorter than or as long as scape 63
63 Tergite 2 at most as long as anterior width (Fig. 81) Heliodon
Tergite 2 more than twice as long as anterior width (Fig. 347) Rhopalosyrphus (s.l.) oreokawensis
64 Vertex convex, shining, sparsely pilose to bare (Fig. 310, 315) Pseudomicrodon
Vertex more or less flat, dull and entirely pilose (Fig. 339, 344) 65
65 Tergite 2 with anterior margin about as wide as posterior margin (Fig. 295) Peradon: trivittatum-group
Tergite 2 with anterior margin at least 1.5 times as wide as posterior margin (Fig. 332, 337, 342) 66
66 Katepimeron pilose (sometimes only along anterior margin) Rhopalosyrphus s.s.
Katepimeron bare Rhopalosyrphus s.l.
67 Abdomen oval or elongate, not constricted in dorsal view (Fig. 35, 269, 293, 294) 69
Abdomen constricted in dorsal view (i.e. with narrowest point (in dorsal view) at tergite 2 and widest point at tergite 3 or 4) (Fig. 271, 272, 276) 68
68 Postero-apical corner of wing cell r4+5 widely rounded. Segment 2 longer than thorax (Fig. 59) Ceriomicrodon petiolatus
Postero-apical corner of wing cell r4+5 more or less rectangular or acute, with small appendix (Fig. 271). Segment 2 usually shorter than or as long as thorax (Figs 269, 284) (except in one undescribed African taxon) Paramixogaster (in part)
69 Basoflagellomere about six times as long as scape (Fig. 36) Bardistopus
Basoflagellomere at most four times as long as scape 70
70 Abdomen about as long as wide, with tergite 2 about as long as tergites 3 and 4 together (Fig. 397, 398) Sulcodon
Abdomen at least 1.5 times as long as wide, with tergite 2 less than half as long as tergites 3 and 4 together 71
71 Face medially with vitta of transversely wrinkled texture (Fig. 291) Peradon: flavofascium-group (in part)
Face medially smooth 72
72 Basoflagellomere longer than scape Paramixogaster (in part: Paramixogaster acantholepidis, Paramixogaster crematogastri)
Basoflagellomere shorter than scape 73
73 Tergite 2 twice as wide as long or wider; entirely black Metadon (in part: Metadon bifasciatus)
Tergite 2 about 1.5 times as wide as long; with large yellow marking in shape of an inverted “V” Microdon trigonospilus Bezzi
74 Vein M anteriorly without small stump extending into cell r4+5 (Fig. 3, 389, 404) 76
Vein M anteriorly with small stump extending into cell r4+5 (Fig. 28, 242, 244) 75
75 Crossvein r-m located between basal 1/4 and 1/3 of cell dm (Fig. 242, 244) Mixogaster
Crossvein r-m located within basal 1/7 of cell dm (Fig. 28) Aristosyrphus (in part: some specimens of Aristosyrphus primus)
76 Face with median tubercle on dorsal half (Fig. 31) Aristosyrphus (Eurypterosyrphus)
Face without median tubercle (Fig. 5) 77
77 Vein M1 more or less straight, not parallel to wing margin, making straight angle with vein R4+5 (Fig. 14, 166, 219) 79
Vein M1 at least in anterior half (sometimes also in posterior half) oblique, more or less parallel to wing margin, making acute angle with vein R4+5 (Fig. 3, 28) 78
78 Abdomen constricted or parallel-sided, not or only slightly wider than thorax (Fig. 27) Aristosyrphus s.s.
Abdomen oval, clearly wider than thorax (cf. Fig. 7, 20) Afromicrodon
79 Abdomen constricted (i.e. with narrowest point at tergite 2 and widest point at tergite 3 or 4) or elongate and parallel-sided (Figs 103, 262, 284) 89
Abdomen oval (Figs 7, 10, 20, 401) or tapering / triangular (Figs 388, 392) (tergite 2 may be quite narrow anteriorly, but then the abdomen does not get wider beyond posterior margin of tergite 2) 80
80 Sternites 2 and 3 (often also 1 and 2) separated by unusually wide membraneous part, about as wide as sternite 2 medially or wider (Figs 393, 394). Antetergite of tergite 1 enlarged, longer than tergite 1 medially, almost at level with tergite 1 Stipomorpha
Sternites 2 and 3 not separated by unusually wide membraneous part. Antetergite small, shorter than or as long as tergite 1 medially, often not at level with tergite 1 but making a smaller angle 81
81 Basoflagellomere shorter than or as long as scape (basoflagellomere never furcate) 93
Basoflagellomere longer than scape (basoflagellomere sometimes furcate in male) 82
82 Antenna at least as long as distance between antennal fossa and anterior oral margin, furcate in male (Figs 39, 77, 138, 144, 356–361) 86
Antenna shorter than distance between antennal fossa and anterior oral margin, never furcate 83
83 Thorax and abdomen black Archimicrodon s.l. (undescribed taxa from Papua New Guinea)
Thorax and abdomen yellow and black 84
84 Postpronotum bare Surimyia
Postpronotum pilose 85
85 Position of crossvein r-m at same level as bm-cu (Fig. 258) Paragodon
Position of crossvein r-m more apical: approximately at basal 1/8 of cell dm Hypselosyrphus (in part)
86 Scutellum sulcate apicomedially (cf. Fig. 183) 88
Scutellum not sulcate apicomedially, more or less semicircular 87
87 Antenna inserted dorsally on head: at or above dorsal eye margin. Male basoflagellomere multifurcate (Figs 138, 142–144, 149) Masarygus
Antenna inserted below dorsal eye margin. Male basoflagellomere bifurcate (Figs 356–360) Schizoceratomyia
88 Katepisternum pilose. Metasternum developed and pilose Furcantenna
Katepisternum bare. Metasternum underdeveloped and bare Carreramyia
89 Postpronotum pilose 91
Postpronotum bare 90
90 Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere more than 3 times as long as wide (Figs 269–277) Paramixogaster (in part: Paramixogaster decipiens (de Meijere) and undescribed Australian sp.)
Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere less than 2 times as long as wide (Figs 301, 302, 306) Piruwa
91 Mesoscutum with transverse suture complete (reaching from one notopleuron to the other) Indascia
Mesoscutum with transverse suture not complete (not visible medially) 92
92 Antenna longer than distance between antennal fossa and anterior oral margin. Male basoflagellomere bifurcate (Figs 430, 432) Undescribed genus #2, species MCR-02
Antenna shorter than distance between antennal fossa and anterior oral margin. Male basoflagellomere not furcate (Figs 262–266) Paramicrodon
93 Katepimeron pilose Hypselosyrphus ulopodus
Katepimeron bare 94
94 Occiput wide, both dorsally and ventrally (Fig. 328) Rhoga
Occiput narrow, at least on ventral half (Figs 5, 229, 403) 95
95 Postpronotum bare Surimyia
Postpronotum pilose 96
96 Vertex not produced, more or less flat (Figs 3–5) Afromicrodon
Vertex produced, more or less convex (Figs 99, 100) Hypselosyrphus
97 Abdomen oval or more or less parallel-sided, not constricted (Fig. 330). Occiput without creases (Fig. 328) Rhoga (in part: maculata, mellea, sepulchrasilva)
Abdomen elongate and constricted (narrowest point at transition between tergites 2 and 3) (Figs 377, 382). Occiput with distinct creases (Figs 379, 384) 98
98 Proanepisternum without row of long stiff pile. Eye bare Spheginobaccha (perialla-group)
Proanepisternum with row of long stiff pile. Eye bare or pilose 99
99 Eye pilose. Alula microtrichose Spheginobaccha (macropoda-group)
Eye bare. Alula partially bare Spheginobaccha (rotundiceps-group)
Genera accounts
Order and format

The genera accounts are presented in alphabetic order. Accounts are only given for taxa considered as valid genera or subgenera. Synonyms and misspelled names can be found under the valid genera to which they belong. Each group account starts with information on the original description and the type species. This is followed by the following components.

Description. Body length (intended only as an approximation, as not all specimens have been measured). A short characterization of the habitus is given, followed by a general description, which is intended to give characters considered (potentially) useful for identification, and to indicate the variability of characters. Unless stated otherwise, all listed characters apply to both sexes. Illustrations are given to illustrate habitus, important external characters and male genitalia. Additional morphological characters can be found in the character matrix of Reemer and Ståhls (in press).

Diagnosis. The shortest possible enumeration of external characters considered sufficient to distinguish the genus from all other Microdontinae. Characters of the male genitalia are only given in a few cases. The combination of the given characters is necessary for the diagnosis; all characters not given are considered unnecessary for this purpose. In some cases this diagnosis will not add much to the characters given in the key, but in other cases it will provide a ‘short-cut’ to the recognition of the genus.

Discussion. Arguments are given for the proposed classification. Other comments are given when necessary, e.g. on type specimens, history of classification, and morphological characters.

Diversity and distribution. The number of described species is given, sometimes with a speculation on the possible number of undescribed species. When available, a reference to species keys is given. The known geographic range is indicated.

Etymology. Only given for newly described genera.

Afromicrodon Thompson

http://species-id.net/wiki/Afromicrodon

Figs 3–6
Afromicrodon Thompson, 2008: 26 (in Cheng and Thompson 2008). Type species: Microdon johannae van Doesburg, 1957: 109, by original designation.
Description.

Body length: 6–9 mm. Relatively small flies with short antennae and oval abdomen. Head slightly wider than thorax. Face evenly convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput narrow over entire length. Eye bare. Eyes in male strongly approaching each other at level of frons; with mutual distance about equal to width of antennal fossa. Antennal fossa about as high as wide. Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere approximately as long as scape; oval, short; bare. Postpronotum pilose. Anepisternum without sulcus; pilose, except bare on ventral 1/4. Anepimeron pilose on dorsal half, bare on ventral half. Katepimeron convex; bare. Scutellum semicircular; without calcars. Wing: vein R4+5 without appendix; vein M1 anterior half directed somewhat outward, making acute angle with R4+5, posterior half perpendicular to vein M; crossvein r-m located around basal 1/4 of cell dm. Abdomen oval. Male genitalia: phallus straight, not furcate; hypandrium with bulb-like base and basolateral bulges; epandrium without ventrolateral ridge; surstylus large: about as long as hypandrium, somewhat sickle-shaped.

Diagnosis.

Vertex flat. Occiput narrow. Antenna shorter than distance between antennal fossa and anterior oral margin. Postpronotum pilose. Katepimeron bare. Vein R4+5 without posterior appendix. Abdomen oval.

Diversity and distribution.

Described species: 5. Restricted to Madagascar and the Comorean islands.

Archimicrodon Hull

http://species-id.net/wiki/Archimicrodon

Figs 7–26
Archimicrodon Hull, 1945: 75. Type species: Microdon digitator Hull, 1937: 19, by original designation.
Subgenus: Hovamicrodon Keiser, 1971: 248. Type species: Hovamicrodon silvester Keiser, 1971: 251, by original designation. stat. n.
Description.

Body length: 4–11 mm. Small to moderately sized flies with short antennae and oval abdomen. Head about as wide as thorax or slightly wider. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male strongly converging at level of frons, with mutual distance about as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin; basoflagellomere as long as or longer than scape, oval, sometimes with acute apex and concave dorsal margin; bare. Postpronotum pilose. Scutellum semicircular; with or without calcars, sometimes apicomedially sulcate; in subgenus Hovamicrodon calcars are spatulate (spoon-shaped). Anepisternum weakly sulcate; pilose anteriorly and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 with or without posterior appendix (this appendix only lacks in certain undescribed species from New Guinea); vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located around basal 1/5 to 1/4 of cell dm. Abdomen oval, about 1.5 to 2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus furcate, with furcation point near apex; hypandrium with basal part bulb-like; epandrium without ventrolateral ridge; surstylus unfurcate.

Diagnosis.

Abdomen oval. Antenna shorter than distance between antennal fossa and anterior oral margin. Postpronotum pilose. Postero-apical corner of cell r4+5 rectangular. Proepimeron bare. Anepisternum widely bare medially, also on dorsal half. Anepimeron entirely pilose. Vein R4+5 usually with posterior appendix; if not: thorax and abdomen entirely black.

Discussion.

Archimicrodon was described as a subgenus of Microdon by Hull (1945), and considered as such by subsequent authors, including Cheng and Thompson (2005), who stated that three species are included. Most of the species assigned to Archimicrodon in the present paper were previously placed in Microdon. However, they do not agree with the more strict definition of Microdon used here. Its independent position from Microdon and its monophyly are supported by the phylogenetic results of Reemer and Ståhls (in press). These are reasons to raise Archimicrodon to generic status.

Three groups are recognized within this genus: Archimicrodon s.s., the subgenus Hovamicrodon, and a ‘leftover’ group, here called Archmicrodon s.l. Archmicrodon s.s. is based on Archmicrodon simplicicornis (de Meijere, 1908), a subjective senior synonym of the type species of the genus, Microdon digitator Hull, 1937 syn. n. Archimicrodon s.s. is here defined by the shape of the surstylus: more or less oval, without a long posterior process (Fig 9, 15); scutellar calcars are either present or absent, but never spatulate. The subgenus Hovamicrodon is defined (following Keiser 1971) by the spatulate shape of the scutellar calcars (Fig. 18); the surstylus has a long posterior process (Fig. 19). Archimicrodon s.l. is here defined as containing all other species, in which the scutellar calcars are absent or - if present - not spatulate, and in which the surstylus has a long posterior process (Figs 22–26). As far as the African species are concerned, this group corresponds with the brevicornis-group of Bezzi (1915).

The three groups are very similar in their morphology, except for the small differences as noted above. It seems likely that the groups are closely related. The subgenus Hovamicrodon is probably monophyletic, considering the spatulate scutellar calcars in combination with its restricted distribution (Madagascar). However, as the phylogenetic analyses by Reemer and Ståhls (in press) indicate, it is so closely related to Archimicrodon s.l. (which is recovered as paraphyletic with respect to Hovamicrodon) that a separate generic status seems not warranted. Besides, a spatulate shape of the scutellar calcars can also be found in certain species of the New World genera Laetodon gen. n. and Serichlamys Curran, 1925. The latter genus is recovered as sister to Archimicrodon by Reemer and Ståhls (in press). As this character is not unique, it does not provide sufficient basis to base a genus on.

Sexual dimorphism can be pronounced, especially in the African species of this group (including Hovamicrodon). Females tend to be much larger than males, and are different in colouration (usually darker). As several species were described from one sex only (such as certain Madagascar species described by Keiser 1971), it is possible that some of these species are actually synonyms. However, as many taxa are represented by only one specimen, these matters cannot yet be resolved.

Hova is the name of one of the social castes of the Merina, an ethnic group indigenous to Madagascar. Keiser (1971) used this name for his genus Hovamicrodon. Surprisingly, he did not include the Madagascar species Microdon hova Hervé-Bazin, 1913 in this genus, although this species clearly belongs to this group (spatulate scutellar calcars). Keiser (1971) does mention a specimen which he believes to be Microdon hova, based on the description, but for some reason this species is not listed under Hovamicrodon. However, when Keiser died in 1969, his paper was not finished yet. It was published posthumously, after the manuscript was finished and submitted by E. Lindner. Therefore, it is seems possible that Keiser intended to include Microdon hova in Hovamicrodon.

Notes on species.

In genitalia, Microdon browni Thompson, 1968 is similar to Archimicrodon s.l.: phallus short, apically furcate, with dorsobasal projection; hypandrium with bulb-like base; surstylus with two elongate lobes; epandrium without ventrolateral ridge. In external morphology, the only difference with Archimicrodon seems to be that the antennae are longer than the distance between the antennal fossa and the anterior oral margin. This character is considered not important enough for group definition, as antennal length is quite variable within many genera of Microdontinae. For these reasons, Microdon browni is here considered as a species of Archimicrodon s.l. The phylogenetic analysis of morphological characters by Reemer and Ståhls (in press) provides no further clue to the taxonomic affinities of this taxon.

Diversity and distribution.

Described species: 45. Widely distributed in the Afrotropical, Oriental and Australasian regions, with one species known from the Eastern Palaearctic (Archimicrodon simplex (Shiraki, 1930)). Archimicrodon s.s. is only known from the Oriental region. The number of species of Archimicrodon s.s. is not known, as the male genitalia of several species were not studied. The subgenus Hovamicrodon (six species) is restricted to Madagascar.

Aristosyrphus Curran

http://species-id.net/wiki/Aristosyrphus

Figs 27–34
Aristosyrphus Curran, 1941: 247. Type species: Aristosyrphus primus Curran, 1941: 252, by original designation.
Protoceratophya Hull, 1949: 314. Type species: Ceratophya carpenteri Hull, 1945: 76, by original designation. For synonymy see Cheng and Thompson (2008).
Paraceratophya Fluke, 1957: 38. Misspelling of Protoceratophya Hull.
Subgenus:Eurypterosyrphus Barretto & Lane, 1947: 141. Type species: Eurypterosyrphus melanopterus Barretto & Lane, 142, by original designation. Status as subgenus: Cheng and Thompson (2008).
Description.

Aristosyrphus (Aristosyrphus). Body length: 6–18 mm. Slender flies, often with constricted abdomen. Head wider than thorax. Face convex or almost straight in profile; about as wide as an eye or narrower. Lateral oral margins not produced. Vertex flat. Occiput narrow over entire length. Eye bare. Eyes in male weakly converging at level of frons, with mutual distance 2 to 3 times the width of antennal fossa. Antennal fossa about as wide as high. Antenna longer or shorter than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum without or with weak sulcus; anteriorly pilose or bare, posteriorly pilose, with pile limited to dorsal half. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 making acute angle with vein R4+5, anterior part or entire vein M1 parallel to wing margin; postero-apical corner of cell r4+5 angular, with small appendix; crossvein r-m located within basal 1/7 of cell dm, often very close to base. Abdomen elongate: slightly oval, parallel-sided or constricted at segment 2; more than twice as long as wide. Tergites 3 and 4 fused. Male genitalia: phallus unfurcate, straight or bent dorsad; ejaculatory hood apicodorsally separately developed from actual phallus into prong-like structure, which may be mistaken for dorsal aedeagal process, but does not contain a sperm-duct; apical part of hypandrium consists of two separate lobes (separated ventromedially); epandrium without ventrolateral ridge; surstylus furcate or unfurcate.

Description.

Aristosyrphus (Eurypterosyrphus) Body length: 8-14 mm. Slender flies with parallel-sided, constricted or kite-shaped abdomen. Head wider than thorax. Face more or less straight, with median tubercle on dorsal half; about as wide as an eye or narrower. Vertex flat. Occiput narrow over entire length. Eye bare. Eyes in male not or only slightly converging at level of frons, with mutual distance 4 to 5 times the width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter or longer than scape, oval, sometimes appearing swollen: more than twice as wide as scape; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum without or with weak sulcus; pilose on dorsal half, bare ventrally. Anepimeron pilose on dorsal half, bare ventrally. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 making straight or acute angle with vein R4+5; postero-apical corner of cell r4+5 angular, with small appendix; crossvein r-m located around basal 1/3 of cell dm. Abdomen parallel-sided, constricted or kite-shaped; more than twice as long as wide. Tergites 3 and 4 fused. Male genitalia: phallus unfurcate, straight or bent dorsad; ejaculatory hood apicodorsally enveloping phallus; apical part of hypandrium consists of two separate lobes (separated ventromedially); hypandrium in some species with elongate ventromedian structure parallel to phallus Figs 32, 34), resembling the lingula of certain taxa of the subfamily Syrphinae; epandrium without ventrolateral ridge; surstylus furcate or unfurcate.

Diagnosis.

Vein R4+5 without posterior appendix. Abdomen elongate and parallel-sided or constricted. Postpronotum pilose. Mesoscutum with transverse suture incomplete. Antenna longer than distance between antennal fossa and anterior oral margin.

Aristosyrphus s.s. Vein M1 oblique, at least anterior half parallel to wing margin. Face evenly convex. Anepimeron entirely pilose. Crossvein r-m located around basal 1/3 of cell dm. Ejaculatory hood apicodorsally developed into prong-like structure, separate from actual phallus (phallus may seem furcate under casual observation, but ejaculatory hood does not contain sperm duct).

Eurypterosyrphus. Vein M1 oblique or straight. Face with median tubercle. Anepimeron bare on ventral half. Crossvein r-m located within basal 1/7 of cell dm. Ejaculatory hood apicodorsally enveloping phallus, not developed into separate, prong-like structure.

Discussion.

Morphological variation within this group is large, especially in the male genitalia (Figs 29, 32–34). In some specimens of Aristosyrphus primus Curran, 1941 an anterior stump is present at vein M (Fig. 28). This character has always been used as diagnostic for Mixogaster (Hull 1954, Cheng and Thompson 2008).

Diversity and distribution.

Described species: 7 (Aristosyrphus s.s.: 4; Eurypterosyrphus: 3). Several undescribed species are known to the first author. Central and South America.

Bardistopus Mann

http://species-id.net/wiki/Bardistopus

Figs 35–37
Bardistopus Mann, 1920: 61. Type species: Bardistopus papuanum Mann, 1920: 61, by original designation.
Description.

Body length: 6–7 mm. Small, dark flies with very long antennae and oval abdomen, which in lateral view appears constricted. Head slightly wider than thorax. Face evenly convex. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow; dorsally slightly widened. Eye bare. Eyes in male not converging at level of frons; mutual distance much larger than width of antennal fossa. Antennal fossa about as high as wide. Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere about six times as long as scape. Postpronotum bare. Scutellum semicircular; without calcars. Anepisternum without sulcus; pilose anteriorly and posteriorly, widely bare in between. Anepimeron pilose on dorsal half, bare on ventral half. Katepimeron flat; pilose. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5 and vein M; crossvein r-m located around basal 1/7 of cell dm. Abdomen oval in dorsal view, but in lateral view appearing constricted due to flattened segment 2. Tergites 3 and 4 fused. Male genitalia: phallus furcate, with furcation point in apical half, strongly bent dorsad; epandrium without ventrolateral ridge; surstylus elongate, bent dorsad.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum bare. Abdomen in dorsal view oval; in lateral view constricted at segment 2. Basoflagellomere about six times as long as scape.

Discussion.

No statements about taxonomic affinities of Bardistopus have been made previously, except Cheng and Thompson (2008) who wrote that the name was ‘established for a Microdon species, which has a greatly elongate basoflagellomere’. Clearly the taxon does not belong to Microdon, because of the long basoflagellomere and the structure of the male genitalia (apically furcate phallus). These characters, combined with the bare postpronotum, suggest it might be related to Paramixogaster. However, the phylogenetic analysis of morphological characters by Reemer and Ståhls (in press) place it as a sister group of a clade containing taxa of which the male has a furcate basoflagellomere: Schizoceratomyia, Furcantenna and Carreramyia. Future studies employing molecular data could help elucidate the phylogenetic affinities of Bardistopus.

According to Mann (1920) the type specimens of the type species are females, but actually both are males (coll. USNM).

Diversity and distribution.

Described species: 1. Solomon Islands: Ugi.

Carreramyia Doesburg, stat. n.

http://species-id.net/wiki/Carreramyia

Figs 38–41
Carreramyia van Doesburg, 1966: 93. Type species: Microdon megacephalus Shannon, 1925: 213, by original designation.
Description.

Body length: 5–8 mm. Yellowish brown or black flies, tergites sometimes yellow with dark vittae. Mimics of stingless, Trigona-like bees (Apidae: Meliponini), due to the brush-like pilosity of the hind tibiae and the more or less triangular abdomen. Head wider than thorax. Face more or less straight in profile; wider than eye. Lateral oral margins not produced. Vertex strongly produced. Occiput ventrally narrow, dorsally widened. Eye bare. Eyes in male not approaching each other; separated over distance much wider than antennal fossa. Antennal fossa about as high as wide. Antenna longer than distance between antennal fossa and anterior oral margin. Antenna inserted below dorsal eye margin; basoflagellomere at least four times as long as scape, bifurcate in male, unfurcate in female; bare. Postpronotum pilose. Anepisternum without sulcus; continually pilose on dorsal half, bare on ventral half. Anepimeron pilose on dorsal half, bare on ventral half. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 perpendicular to R4+5 and M; crossvein r-m located close to bm-cu. Abdomen more or less triangular, with tergites 3 and 4 narrower than tergite 2. Tergites 3 and 4 fused. Sternite 1 bare or pilose. Male genitalia: phallus straight, furcate near apex; hypandrium with bulb-like base and basolateral bulges; epandrium without ventrolateral ridge.

Diagnosis.

Hind tibia widened and with long, brush-like pilosity. Vein R4+5 without posterior appendix. Vertex strongly produced but not shining and convex. Basoflagellomere at least four times as long as scape, bifurcate in male.

Diversity and distribution.

Described species: 2. Only the type species, Carreramyia megacephalus (Shannon, 1925), is known from more than one specimen (Panama and Costa Rica). The other species was found in Peru. Descriptions of two additional species from Peru and Surinam are in preparation by the first author. Apparently the genus is widespread in the Neotropical region.

Ceratophya Wiedemann

http://species-id.net/wiki/Ceratophya

Figs 42–45
Ceratophya Wiedemann, 1824: 14. Type species Ceratophya notata Wiedemann, 1824: 14, by subsequent designation of Blanchard (1846: 145).
Ceratophyia Osten Sacken, 1858: 46. Misspelling.
Description.

Body length: 7–9 mm. Relatively small, black and yellow flies with long antennae and oval abdomen. Face in profile straight, with anterior oral margin somewhat produced ventrad; laterally depressed, therefore slightly carinate medially; somewhat wider than an eye. Lateral oral margins not produced. Vertex flat. Occiput narrow ventrally, slightly widened dorsally. Eye bare. Eyes in male not approaching each other, eye margins parallel; mutual distance much larger than width of antennal fossa. Antennal fossa about as high as wide. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape; elongate, oval. Postpronotum pilose. Anepisternum with shallow sulcus; entirely short pilose, except bare on ventral 1/4. Anepimeron entirely pilose. Katepimeron weakly convex; bare. Scutellum semicircular or apicomedially sulcate; without calcars. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5 and vein M. Legs: hind tibia somewhat swollen; hind metatarsus enlarged, quadrate, sometimes with strong basoventral tooth. Abdomen with tergite 4 in lateral view more or less perpendicular to tergite 2. Tergites 3 and 4 not fused, able to articulate independently; in female with posterior margin of tergite 3 strongly overlapping tergite 4. Male genitalia: phallus strongly bent dorsally, furcate basally, with ejaculatory hood dorsally strongly elongate and thus forming a third process about equally long as two aedeagal processes; epandrium with ventrolateral ridges.

Diagnosis.

Tergites 3 and 4 not fused, strongly overlapping. Tergite 4 in lateral view more or less perpendicular to tergite 2. Basoflagellomere bare; longer than scape.

Discussion.

Cheng and Thompson (2008) point out the confused taxonomic history of Ceratophya. Unlike these authors, who consider the group as a subgroup of Microdon, it here treated as a separate genus. This is done because of the phylogenetic results of Reemer and Ståhls (in press) and because it does not agree with the diagnosis of Microdon as defined in the present paper.

Diversity and distribution.

Described species: 4. Description of one additional species from Argentina is in preparation by the first author. Known from Central and South America (Panama to northern Argentina).

Ceratrichomyia Séguy, stat. n.

http://species-id.net/wiki/Ceratrichomyia

Figs 46–58
Ceratrichomyia Séguy, 1951: 14. Type species: Ceratrichomyia behara Séguy, 1951: 14, by original designation.
Description.

Body length: 7–10 mm. Slender, black flies with yellow markings and a constricted abdomen. Head wider than thorax, face and vertex wider than an eye. Face ventrally produced in profile; wider than an eye. Lateral oral margins not produced. Vertex swollen. Occiput narrow ventrally, strongly widened dorsally. Eye bare. Eyes in male not approaching each other; smallest mutual distance much larger than width of antennal fossa. Antennal fossa about as high as wide. Antenna longer than height of head. Basoflagellomere at least three times as long as scape; with long pilosity. Postpronotum pilose or bare. Mesoscutum with transverse suture complete. Scutellum without calcars. Anepisternum with deep sulcus; entirely pilose. Anepimeron entirely pilose. Katepimeron convex; pilose or bare. Wing: vein R4+5 with posterior appendix; vein M1 straight, perpendicular to R4+5 and M; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located around basal 1/4 of cell dm. Abdomen constricted at segment 2. Tergites 3 and 4 not fused, able to articulate independently. Sternite 1 bare. Sternite 4 in male covered by genital capsule, therefore not visible without removing genitalia. Male genitalia: phallus straight or slightly bent dorsad, with spherical base very large, at least as long as remaining part of phallus; phallus furcate near apex; epandrium with or without ventrolateral ridge; surstylus deeply furcate.

Diagnosis. The combination of a complete transverse suture on the mesoscutum and a constricted abdomen is only found in Ceratrichomyia, Indascia Keiser, Indascia, 1958, Thompsodon gen. n. and certain species of Paramixogaster Brunetti, 1923. Males are easily distinguished from all these taxa by the long pilosity of the basoflagellomere, and also by sternite 4, which is covered by the genital capsule. From Paramixogaster this genus also differs by the unfused tergites 3 and 4. Females are unknown.

Discussion. Séguy (1951) attributed one species to this genus. He designated a male and a female as ‘types’, and another male as ‘cotype’. These are here all considered as syntypes. Examination of these three specimens made clear that they belong to three different species, which makes it necessary to designate a lectotype. The male with the following label data is here designated as lectotype. Label 1: “Madagascar, Behara”; label 2 (blue): “Museum Paris, III-38, A. Seyrig”; label 3 (red): “Type”; label 4: “Ceratrichomyia behara type du genre [male symbol] Séguy 50”; coll. MNHN. A redescription of the lecotype is given in the next section of the present paper. By this lectotype designation, the other two syntypes become paralectotypes. The male collected in Bekily (Madagascar) belongs to a new species of Ceratrichomyia, which is described in the present paper as Ceratrichomyia bullabucca spec. n. The female paralectotype, collected in Bekily, is here considered to belong to a previously undescribed species of Paramixogaster, because it possesses all characters described as diagnostic for that genus (see genus account). A description of that species is given under the name Paramixogaster piptotus sp. n. A third species attributed to this genus, Ceratrichomyia angolensis sp. n., is described from Angola.

The long pilosity of the male basoflagellomere was used by Séguy (1951) as a character to set his African genus Ceratrichomyia apart from other Microdontinae. This character is also present in Ptilobactrum Bezzi, 1915, another African taxon. Apparently Séguy was not aware of this, as he did not refer to Ptilobactrum. Cheng and Thompson (2008) did notice the similarity in antennal structure in both taxa and, based on the descriptions, proposed to regard Ceratrichomyia as a subjective junior synonym of Ptilobactrum.

Study of the type specimens of Ceratricomyia and Ptilobactrum revealed that these taxa are in fact very different. While Ceratrichomyia has, for instance, a constricted abdomen with unfused tergites 3 and 4, Ptilobactrum has a conical abdomen with fused tergites 3 and 4. The structures of the male genitalia are also very different (compare Figs 56–58 with 326), e.g. with a deeply furcate surstylus in Ceratrichomyia and an unfurcate one in Ptilobactrum. Considering these morphological differences, and supported by the phylogenetic results of Reemer and Ståhls (in press), Ceratrichomyia is here re-instated as a valid genus.

Diversity and distribution. Described species: 3. Two species are known from Madagascar, one from the African mainland (Angola).

Ceriomicrodon Hull

http://species-id.net/wiki/Ceriomicrodon

Figs 59–60
Ceriomicrodon Hull, 1937a: 25. Type species: Ceriomicrodon petiolatus Hull, 1937: 25, by original designation.
Description.

Body length: 11 mm. Very slender, wasp-like flies with long antennae and constricted abdomen. Face convex, somewhat produced on ventral half; narrower than an eye. Lateral oral margins clearly produced. Vertex flat. Occiput ventrally narrow, dorsally somewhat widened. Eye bare; frontally with narrow, horizontal area of enlarged ommatidia at level of antenna. Eyes in male strongly convergent at level of frons. Antennal fossa about 1.5 times as wide as high. Antenna longer than height of head; basoflagellomere more than twice as long as scape; bare. Postpronotum bare. Anepisternum with shallow sulcus; pilose along posterior margin and sparsely anterodorsally, widely bare in between. Anepimeron entirely pilose. Katepimeron flat; bare. Scutellum semicircular; without calcars. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded; crossvein r-m located around basal 1/3 of cell dm. Abdomen very slender, constricted at tergite 2. Tergite 2 longer than thorax, about as long as tergites 3-5 together. Tergites 3 and 4 fused. Male genitalia: phallus furcate near apex, with dorsal process long and whip-like, ventral process very short; epandrium with ventrolateral ridge.

Diagnosis.

Postpronotum bare. Vein R4+5 with posterior appendix. Postero-apical corner of cell r4+5 widely rounded. Abdomen constricted. Tergite 2 longer than thorax.

Discussion.

Ceriomicrodon is treated as a subgenus of Microdon by Thompson et al. (1976) and Cheng and Thompson (2008). However, it does not agree with the diagnosis of Microdon as used in the present paper, because of several characters (e.g. postpronotum bare, abdomen petiolate, phallus with dorsal process long and whip-like). In addition, the phylogenetic results of Reemer and Ståhls (in press) indicate a relationship with e.g. Pseudomicrodon and Rhopalosyrphus.

Diversity and distribution.

Described species: 1. Known from Central (Mato Grosso) and Northern Brazil (Roraima).

Cervicorniphora Hull, stat. n.

http://species-id.net/wiki/Cervicorniphora

Figs 61–62
Cervicorniphora Hull, 1945: 75. Type species: Microdon alcicornis Ferguson, 1926a: 171, by original designation.
Description.

Body length: 8 mm. Broadly built flies with oval abdomen. Head wider than thorax. Face convex in profile; wider than an eye. Lateral oral margins not produced. Antennal fossa about as wide as high. Vertex flat. Occiput rather wide, dorsally strongly widened. Eye bare. Eye margins in male not converging at level of frons; with mutual distance about five times the width of antennal fossa. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, bare, bifurcate, with dorsal branch narrower and shorter than ventral branch, ventral branch strongly curved; arista well-developed. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum moderately sulcate; pilose anteriorly and posteriorly, bare medially. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded; crossvein r-m located around basal 1/4 of cell dm. Abdomen oval, about 1.5 times as long as wide. Tergites 3 and 4 fused. Male genitalia: phallus unfurcate; epandrium without ventrolateral ridge; surstylus with long posterior process and wide anterior lamella. Female unknown.

Diagnosis.

Basoflagellomere bifurcate. Vein R4+5 with posterior appendix.

Discussion.

Although Ferguson (1926a) argued that the furcate antenna provides insufficient basis for erecting a new genus for Microdon alcicornis, Hull (1945) decided to erect Cervicorniphora for this species, as a subgenus of Microdon. Cheng and Thompson (2008) also considered this genus-group as a subgenus of Microdon. The phylogenetic analysis of morphological characters by Reemer and Ståhls (in press) did not provide many clues as to the taxonomic affinities of this taxon, although it seems clear that it is not related to other taxa in which the male has a furcate basoflagellomere. As the characters of Cervicorniphora (e.g. phallus not furcate) do not fit in the concept of Microdon s.s. (phallus furcate near base) as defined in the current paper, Cervicorniphora is here raised to genus rank, to avoid disrupting the monophyly of Microdon.

The female is unknown. In most other microdontine taxa in which the male has a furcate basoflagellomere (e.g. Carreramyia, Schizoceratomyia), the female has an unfurcate basoflagellomere. So, the possibility that the female of Cervicorniphora has unfurcate antennae should be taken into account.

Diversity and distribution.

Described species: 1. Australia: New South Wales, Queensland and Tasmania (Ferguson 1926a).

Chrysidimyia Hull

http://species-id.net/wiki/Chrysidimyia

Figs 63–67
Chrysidimyia Hull, 1937b: 116. Type species: Chrysidimyia chrysidimima 1937: 116, by original designation. Name emended by Thompson et al. (1976).
Description.

Body length: 8–10 mm. Metallic green to bluish flies (legs may be yellowish), entire body densely and coarsely punctate, mimics of Chrysididae (Hymenoptera). Head about as wide as thorax. Face convexly produced in profile; about as wide as an eye. Lateral oral margins produced. Vertex flat. Occiput ventrally narrow, dorsally strongly widened. Eye densely pilose. Eyes in male with mutual distance smaller than width of antennal fossa. Antennal fossa twice as wide as high, dorsally covered by ‘shelf-like’ extension of frons. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval; bare. Postpronotum pilose. Notal wing lamina strongly developed; partly overlapping membranes around wing insertion. Scutellum semicircular; with calcars. Anepisternum moderately sulcate; with bare part limited to ventral half. Anepimeron entirely pilose. Katepimeron flat; bare. Katatergum carinate. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded; crossvein r-m located around basal 1/4 of cell dm. Abdomen oval, about 1.5 times as long as wide. Posterior margin of tergite 1 angular. Tergites 3 and 4 fused. Male genitalia: phallus unfurcate; epandrium without ventrolateral ridge; surstylus furcate, with anterior part short and wide, posterior process long and narrow.

Diagnosis.

Head, thorax and abdomen metallic green or blue. Antennal fossa twice as wide as high, dorsally covered by ‘shelf-like’ extension of frons.

Discussion.

Chrysidimyia was treated as a synonym of Microdon by Thompson et al. (1976), but the unfurcate phallus and the phylogenetic results of Reemer and Ståhls (in press) indicate that this status cannot be maitained. Instead, the male genitalia of Chrysidimyia (Fig. 65) resemble those of Laetodon (Fig. 135); these taxa share an unfurcate phallus and a long posterior process on the surstylus. These taxa also have their metallic body colouration and pilose eyes in common. These characters may suggest a phylogenetic relationship, although this is not found by Reemer and Ståhls (in press), who recovered Chrysidimyia in a large polytomy. Besides, the ‘shelf-like’ extension of the frons and dense punctuation of the body are not found in Laetodon. For this reason, we prefer to treat the groups separately.

Diversity and distribution.

Described species: 1. One additional, undescribed species is known to the first author. All known records are from the Amazon region of South America, including the Guyana shield.

Chymophila Macquart (subgenus, see Microdon) Dimeraspis Newman (subgenus, see Microdon)
Type species:

Domodon zodiacus Reemer spec. n. Type locality: Surinam, Paramaribo.

Description.

Body length: 6–8 mm. Moderately small flies with short antennae and oval abdomen. Head a little wider than thorax. Face convex; about as wide as or narrower than an eye. Lateral oral margins weakly produced. Vertex convexly produced, more or less shining, sparsely pilose, almost bare on anterior half. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male weakly converging at level of frons, with mutual distance 3-5 times width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere as long as or longer than scape, bare. Postpronotum pilose. Scutellum semicircular; with calcars. Anepisternum sulcate; pilose anterodorsally and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron almost flat to convex; often with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/6 to 1/4 of cell dm. Abdomen oval, about 1.5 to 2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus furcate near apex, with dorsal process long and whip-like, ventral process very short; epandrium with ventrolateral ridge.

Diagnosis

. Vertex convexly produced. Abdomen oval. Vein R4+5 with posterior appendix. Tergites 3 and 4 fused. Membrane between sternites 2 and 3 much less wide than sternite 2.

Discussion.

All species assigned to this genus were previously undescribed or are still undescribed.

The phylogenetic analysis based on morphology places the type species (Domodon zodiacus sp. n.) in the same clade as Omegasyrphus Giglio-Tos, 1891, Pseudomicrodon Hull, 1937 and Rhopalosyrphus Giglio-Tos, 1891 (Reemer and Ståhls in press). In addition to this phylogenetic evidence, the male genitalia of these taxa are all similar in the structure of the phallus and the shape of the surstylus. Because of the oval, non-constricted abdomen, Domodon species superficially may seem most similar to Omegasyrphus, but differ from that genus by the convex and sparsely pilose vertex, the long antenna, and the medially widely bare anepisternum. With Pseudomicrodon it shares the convex and sparsely pilose vertex, as well as the structure of the male genitalia, but Domodon differs from that genus by the oval (instead of constricted) abdomen.Instead of arbitrarily assigning the species in question to one of the mentioned genera, it is here considered preferable to erect a new genus, so as to emphasize the distinctive features of this group.

Diversity and distribution.

Described species: 1. Surinam. Four additional, undescribed species are known by the first author from French Guyana, Surinam and Costa Rica. Probably the group is widespread in Central and South America.

Etymology.

The generic name is a combination of domus and odon, with the latter used as a suffix derived from Microdon. The Latin word domus is here used in the meaning of ‘dome’ and refers to the convex (dome-shaped) vertex of the species in this genus. The name is to be treated as masculine.

Furcantenna Cheng

http://species-id.net/wiki/Furcantenna

Figs 74–80
Furcantenna Cheng, 2008: 29 (in Cheng and Thompson 2008). Type species: Furcantenna yangi Cheng, 2008: 29, by original designation.
Description.

Body length: 9–10 mm. Broadly built flies with very wide head, long antennae and widened hind tibiae, bee mimics. Head much wider than thorax. Face slightly convex in profile; wider than eye; laterally depressed; medially weakly carinate. Lateral oral margins not produced. Vertex produced. Occiput ventrally narrow, dorsally widened. Eye bare. Eyes in male not convergent at level of frons; separated over distance much larger than width of antennal fossa. Antennal fossa about as high as wide. Antenna much longer than height of head; basoflagellomere bifurcate at base, with ventral branch a little longer than dorsal branch, both branches entirely long pilose; arista absent. Postpronotum pilose. Anepisternum sulcate. Scutellum apicomedially sulcate. Katepisternum dorsally pilose. Metasternum developed and pilose. Wing: vein R4+5 without posterior appendix; vein M1 perpendicular to R4+5 and M; crossvein r-m located around basal 1/5 of cell dm. Hind tibia and tarsus widened. Abdomen oval. Male genitalia: phallus slightly bent dorsad, with large spherical base; phallus furcate near apex; epandrium without ventrolateral ridge; surstylus approximately oval. Females unknown.

Diagnosis.

Male with bifurcate basoflagellomere. Katepisternum pilose. Metasternum pilose.

Diversity and distribution.

Described species: 2. The type species was found in a mountainous area in southeastern China. The second known species, Furcantenna nepalensis sp. n., was collected in the Nepalese Himalaya at an altitude of approximately 1800 meters. The discovery of these species in these areas sheds an interesting light on the biogeography of the taxa with a furcate basoflagellomere in the male. Prior to the description of Furcantenna, such taxa were almost exclusively known from South America (except for the the apparently unrelated Australian Cervicorniphora). The occurrence of the obviously related (Reemer and Ståhls in press) Furcantenna in Oriental mountains on the Asian mainland could possibly be explained as a relict of a wider distribution in early eras.

Type species:

Microdon tricinctus de Meijere, 1908: 208. Type locality: Java.

Description.

Body length: 8–12 mm. Moderately slender to broadly built flies with long antennae; abdomen oval, slightly tapering or basally slightly constricted; often with fasciate patterns of golden pile on thorax and abdomen, sometimes with yellow abdominal markings. Head slightly wider or slightly narrower than thorax. Face convex; narrower than to as wide as an eye. Lateral oral margins produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye short pilose or bare. Eye margins in male converging at level of frons, with mutual distance 1.5–2 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna about as long as distance between antennal fossa and anterior oral margin; basoflagellomere shorter than scape; bare. Postpronotum pilose. Scutellum semicircular; with calcars. Anepisternum sulcate; entirely pilose, except for small bare part ventrally. Anepimeron entirely pilose. Katepimeron convex or nearly flat; with or without wrinkled texture; bare or pilose. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 rounded or rectangular, with or without small appendix; crossvein r-m located between basal 1/6 and 1/5 of cell dm. Abdomen oval or basally constricted, 1.5-3 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus projecting little beyond apex of hypandrium, bent dorsad, furcate with furcation point from halfway to near apex, with both processes about equally long; epandrium without ventrolateral ridge; surstylus with subbasal excavation, dividing surstylus into a basal lamella and a long posterior process.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum pilose. Propleuron bare. Anepisternum almost entirely pilose, at most ventrally with small bare part. Mesonotum with transverse suture incomplete. Basoflagellomere shorter than scape. Tergite 1 long: length/width ratio 1:1.4 to 1:2. Tergite 2: anterior margin less than 1.5 times as wide as posterior margin. Body not entirely metallic green or blue.

Discussion.

All previously described species included in this genus were originally described in the genus Microdon. In the most recent catalogue of Oriental Microdontinae these species were listed under that genus (Knutson et al. 1975). As Microdon is defined more strictly in the present paper, the species can no longer be placed in that genus, hence a new genus is erected. Three new species are described in the present paper.

Diversity and distribution.

Described species: 8. Oriental, ranging from Sri Lanka to Thailand, Vietnam, Java and Borneo.

Etymology.

The generic name is composed of the Greek words helios (sun) and odon, with the latter part used as a suffix derived from Microdon. The first part was chosen to emphasize the Oriental (‘where the sun rises’) distribution of the genus.

Hypselosyrphus Hull, stat. n.

http://species-id.net/wiki/Hypselosyrphus

Figs 97–102
Hypselosyrphus Hull, 1937a: 21. Type species Hypselosyrphus trigonus Hull, 1937: 21, by original designation.
Description.

Body length: 7–10 mm. Stingless bee mimicking flies with short to moderately long antennae and oval to triangular abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex narrow, in most species convexly produced and shining, flat in some species. Occiput narrow over entire length, except ventrally strongly widened in Hypselosyrphus ulopodus. Eye with short, sparse pile. Eye margins in male strongly converging at level of frons, with mutual distance smaller than width of antennal fossa, except 3 times as wide in Hypselosyrphus ulopodus. Antennal fossa about as wide as high. Antenna as long as or shorter than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular, triangular or apicomedially sulcate; without calcars. Anepisternum without or with weak sulcus; pilose anterodorsally and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/8 to 1/4 of cell dm. Abdomen oval or kite-shaped, 1.2 to 2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus furcate near apex, with dorsal process in some species a little longer than ventral process; epandrium with or without ventrolateral ridge.

Diagnosis.

Vein R4+5 without posterior appendix. Crossvein r-m located between basal 1/8 and 1/4 of cell dm. Subcostal vein joins costal vein after level of crossvein r-m. Postpronotum pilose. Abdomen oval or kite-shaped (tergite 2 wide, subsequent tergites triangularly narrowing). Antenna as long as or shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere not furcate. Occiput narrow in dorsal half (usually also in ventral half, except in Hypselosyrphus ulopodus Hull, 1944).

Discussion.

When Hull (1937a) erected the genus Hypselosyrphus for his species trigonus, he mentioned its similarity to Ubristes Walker, 1852 species, without clearly stating the differences. In his key to the groups of Microdontinae, Hull (1949) separated these taxa by the absence (Hypselosyrphus) or presence (Ubristes) of an appendix on vein R4+5. This character serves well to separate Hypselosyrphus from Ubristes s.s. as defined in the present paper, and almost always for Stipomorpha (appendix on vein R4+5 seldomly missing), which was included in Ubristes until now. In later keys and catalogues, Hypselosyrphus was treated as a junior synonym of Ubristes (Thompson 1969, Thompson et al. 1976). Cheng and Thompson (2008) also considered Hypselosyrphus (and Stipomorpha Hull, 1945) synonymous with Ubristes, but nevertheless differentiated the groups in their key. They consider abdominal shape to be diagnostic: oval or rectangular in Ubristes, short, almost equilaterally triangular in Hypselosyrphus, much longer, isosceles triangular in Stipomorpha. As there are many varieties in abdominal shape among the the taxa involved, it is hard to decide where to draw the line. Other characters are necessary to distinguish these taxa satisfyingly (see key and diagnoses).

Diversity and distribution.

Described species: 11. Descriptions of five additional species are in preparation by the first author. Hypselosyrphus is known from Panama, the Amazon region and southern Brazil. Considering the small number of specimens known, it seems likely that the genus is widespread in tropical South America.

Indascia Keiser

http://species-id.net/wiki/Indascia

Figs 103–118
Indascia Keiser, 1958: 221. Type species: Ascia brachystoma Wiedemann, 1824: 33, by original designation.
Description.

Body length: 4–10 mm. Small, slender flies with more or less constricted abdomen. Head wider than thorax. Face convex in profile; narrower than to wider than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally strongly widened. Antennal fossa about as wide as high. Eye bare. Eye margins in male parallel, not converging at level of frons. Antenna shorter to longer than distance between antennal fossa and anterior oral margin. Basoflagellomere as long as to longer than scape, 1.5 to 5 times as long as wide; parallel-sided or with dorsal margin somewhat concave; bare. Postpronotum pilose. Mesoscutum with transverse suture complete. Scutellum semicircular, apex may be slightly acute; without or with very small calcars. Anepisternum convex or sulcate; entirely pilose or with bare part limited to ventral half. Anepimeron entirely pilose. Katepimeron (moderately) convex; bare. Wing: vein R4+5 with or without posterior appendix; vein M1 perpendicular to vein R4+5 and vein M; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located within basal 1/4 of cell dm, sometimes very close to base. Abdomen elongate, at least 3 times as long as wide; constricted, with narrowest point at posterior margin of tergite 2 and widest point at tergite 4. Tergites 3 and 4 not fused. Male genitalia: phallus furcate, with furcation point in distal half; epandrium without ventrolateral ridge; surstylus furcate, with anterior part short, posterior part about twice as long.

Diagnosis.

Abdomen constricted. Postpronotum pilose. Mesoscutum with transverse suture complete. Katepimeron bare. Frons laterally without concave area.

Discussion.

Originally this genus was included in the tribe Sphegini, as part of a subfamily Cheilosiinae (Keiser 1958). Thompson (1969) correctly recognized that it belongs to the Microdontinae, where it has remained since.

Originally, Indascia was based on two species with short antennae and without a posterior appendix on vein R4+5 (Keiser 1958). In two of the species included in the phylogenetic analyses of Reemer and Ståhls (in press) the antennae are long and the appendix on vein R4+5 is present (Indascia gigantica sp. n. and Indascia spathulata sp. n.). Both characters are also found in additional undescribed species known to the first author. Therefore, these characters are considered not to be of diagnostic value for this genus.

Superficially, species of Indascia look similar to those of Paramicrodon de Meijere, 1913 (as noticed by Cheng and Thompson 2008). For discussion on similarities with Paramixogaster Brunetti, 1923 see there.

Diversity and distribution.

Described species: 4. At least four undescribed species are known to the first author. The genus appears to be strictly Oriental, with species known from India, Sri Lanka, Pakistan, Thailand and Vietnam. The origin of the type specimens of the type species (‘India orientalis’) is not exactly known.

Kryptopyga Hull

http://species-id.net/wiki/Kryptopyga

Figs 119–131
Kryptopyga Hull, 1944a: 129. Type species: Kryptopyga pendulosa Hull, 1944a: 130, by original designation.
Description.

Body length: 12–14 mm. Large flies with long antennae (pilose in male) and oval abdomen, which may be constricted basally. Head wider than thorax. Face in profile more or less straight, ventrally produced below eye margin; wider than eye. Lateral oral margins weakly produced. Vertex strongly swollen. Occiput narrow ventrally, strongly widened dorsally. Eye bare. Eyes in male not converging at level of frons; mutual distance about 5 times width of antennal fossa. Antennal fossa about as high as wide. Antenna longer than height of head. Basoflagellomere 3.5-4 (male) or 2.5 (female) times as long as scape; with long pilosity in male, bare in female. Postpronotum pilose. Mesoscutum with transverse suture incomplete. Scutellum semicircular, without calcars. Anepisternum with deep sulcus; pilose anterodorsally and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; with or without wrinkled texture; with rows of microtrichia. Wing: vein R4+5 with posterior appendix; vein M1 in anterior half with outward angle; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/6 and 1/5 of cell dm. Abdomen either oval or somewhat constricted at base, in the latter case with tergite 4 curved downward and more or less perpendicular to tergite 2. Tergites 3 and 4 not fused, able to articulate independently. In male Kryptopyga pendulosa, sternite 4 is covered by the genital capsule and therefore not visible without removing genitalia, while the lateral margins of tergite 3 are strongly curved and ‘tucked away’ under sternite 3 (Fig. 123). Male genitalia: phallus slender, furcate near apex, basally complexly bent into curves, interconnected by a membrane; epandrium without ventrolateral ridge; surstylus approximately oval.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum pilose. Propleuron bare. Mesonotal transverse suture incomplete. Tergites 3 and 4 not fused, able to articulate independently. Anepisternum widely bare of pile (but with microtrichia) medially, also on dorsal half. Male basoflagellomere with long pile.

Discussion.

Hull (1944a) erected the genus and assigned one species to it: Kryptopyga pendulosa Hull, 1944. He considered it close to the African genus Ptilobactrum Bezzi, 1915 because of the long pile on the basoflagellomere, but considered it distinct because of the subpetiolate abdomen and the remarkable structure of the 3rd and 4th abdominal segments. The pilose basoflagellomere in the male is also found in Ceratrichomyia, with which Kryptopyga also shares the swollen vertex and dorsal occiput, and the unfused tergites 3 and 4. The male genitalia, however, are quite different, and in Kryptopyga the mesonotal transverse suture is incomplete.

Together with the Nearctic Microdon craigheidi Walton, 1912, Kryptopyga is the only known taxon of Microdontinae in which the phallus is not simply curved between base and apex, but complexly bent into a couple of curves basally, interconnected by a membrane (compare Fig. 131 with Fig. 232). Despite this common character, there is no reason to suspect a closer relationship between these taxa.

The abdomen in Kryptopyga pendulosa is much more modified than in Kryptopyga sulawesiana sp. n., but the latter species is nevertheless regarded as belonging to the genus based on the pilose basoflagellomere, the shape of the head, the wing venation and the structure of the male genitalia, in which it is all very similar to Kryptopyga pendulosa.

Microdon tuberculatus Shiraki, 1968 might also belong in Kryptopyga, because of its unfused tergites 3 and 4 and similarity in head shape (strongly swollen vertex and dorsal occiput, face ventrally produced below eye margin). However, only the female of this species is known, so it is unknown whether the male has long pile on the basoflagellomere and the characteristic genitalia of Kryptopyga. Therefore, this species is presently left unclassified. As de Meijere (1913) had already used the same species name, the replacement name shirakii is here proposed.

Diversity and distribution.

Described species: 2. Indonesia: Bangka, Java and Sulawesi.

Type species:

Microdon laetus Loew, 1864: 74, by original designation. Type locality: Cuba.

Description.

Body length: 6–9 mm. Small, metallic green to blue flies, with long antennae and oval abdomen. Head about as wide as thorax or slightly wider. Face convex; narrower than an eye. Lateral oral margins weakly produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye pilose. Eye margins in male converging at level of frons, with mutual distance 2 to 4 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna about as long as to longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; with calcars, which may be spatulate (widened and dorsoventrally flattened). Anepisternum weakly sulcate; pilose anteriorly and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/6 to 1/5 of cell dm. Abdomen oval, about 1.5 to 2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus unfurcate, projecting slightly beyond apex of hypandrium; hypandrium with basal part bulb-like; epandrium without ventrolateral ridge; surstylus shallowly furcate, with long posterior process.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum pilose. Abdomen oval. Anepisternum widely bare medially. Propleuron pilose. Postero-apical corner of cell r4+5 rectangular. Eye pilose.

Discussion.

The species included in this genus used to be placed in Microdon (Thompson 1981b). Morphology of the male genitalia, however, is quite distinct from that of Microdon as defined in the present paper: the phallus is short and unfurcate, the epandrium lacks the ventrolateral ridge. Based on these morphological differences and the phylogenetic results of Reemer and Ståhls (in press), Laetodon is here erected as a new genus. See Chrysidimyia for discussion on possible relationships with that genus.

Diversity and distribution.

Described species: 5. Nearctic (4 species) and Neotropical (1 species).

Etymology.

The generic name is composed of laetus and odon, with the first part derived from Microdon laetus Loew, 1864 (the type species of the genus), and the latter used as a suffix derived from Microdon.

Masarygus Brèthes

http://species-id.net/wiki/Masarygus

Figs 136–150
Masarygus Brèthes, 1909: 441. Type species: Masarygus planifrons Brèthes, 1909: 442, by original designation.
Description.

Body length: 4–7 mm. Small, delicate flies with long antennae and flat abdomen. Head slightly to much wider than thorax. Face concave, either entirely or only laterally; wider than an eye. Mouth parts undeveloped: oral opening absent or hardly visible. Vertex more or less flat, not strongly produced or convex. Occiput ventrally narrow or widened, dorsally widened. Eye bare. Eyes in male not converging at level of frons, with mutual distance about 4 times the width of antennal fossa. Antennal fossa about as wide as high or about 1.5 times as wide as high. Antenna as long as or longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, multifurcate in male (3 to 14 branches), unfurcate in female; bare; arista absent in male, present in female. Postpronotum bare. Scutellum semicircular; without calcars. Anepisternum convex; entirely with sparse, bristle-like pile. Anepimeron bare or pilose. Katepimeron convex; bare; with or without wrinkled texture. Wing: vein R4+5 without posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded or rectangular, with or without small appendix; crossvein r-m located very close to base of cell dm (within basal 1/10). Abdomen dorsoventrally flattened; more or less trapezoid, with lateral margins gradually widening posteriad, with largest width at tergite 4; 1.5-2.5 times as long as wide. Tergites 3 and 4 fused. Male genitalia: phallus furcate near apex, straight, projecting not or hardly beyond apex of hypandrium; epandrium without ventrolateral ridge; surstylus unfurcate, more or less oval.

Diagnosis.

Vein R4+5 without posterior appendix. Postpronotum bare. Antenna at least as long as distance between antennal fossa and anterior oral margin. Antenna inserted on head above dorsal eye margin.

Discussion.

Originally, this genus was erected as the first known member of a new family, the Masarygidae (Brèthes 1908; but journal publication was 1909, see Sabrosky 1999). Brèthes associated it with Conopidae and Scenopinidae because of the wing venation, and with Oestridae because of the reduced mouthparts. He also noted a superficial resemblance to certain Stratiomyidae. Bezzi (1910) was the first to recognize Masarygus as belonging to the Syrphidae and related to Microdon, by pointing out its resemblance to Ceratophya and the apparent relationship with ants (as noted by Brèthes 1908). Shannon (1925) considered Masarygus as a synonym of Microdon. Brèthes (1928) objected by pointing out that Masarygus differs from Microdon in the distinct sexual dimorphism and also in wing venation. All subsequent authors have included Masarygus in the Microdontinae.

Masarygus was the first described syrphid taxon with a furcate basoflagellomere (in the male sex only). A few other taxa with this character were described during the 20th century: Schizoceratomyia Carrera, Lopes & Lane, 1947, Johnsoniodon Curran, 1947 and Carreramyia Doesburg, 1966. Masarygus, Schizoceratromyia and Johnsoniodon were considered synonymous by Hull (1949), who also regarded “Masarygus as a Rhoga with fissicorn antennae”, without explicitly including all of these taxa in Rhoga (the oldest name). Papavero (1962) also considered Masarygus, Schizoceratomyia and Johnsoniodon synonymous, because he found that the number of branches on the basoflagellomere (four in Masarygus planifrons, two in the other taxa) was a species-level character rather than a generic character. Van Doesburg (1966) did not agree and considered Masarygus and Schizoceratomyia (including Johnsoniodon) as distinct genera, because of distinct differences in shape of head, antenna and abdomen. Thompson et al. (1976) followed the opinion of Papavero (1962). Cheng and Thompson (2008) considered Masarygus and Schizoceratomyia as distinct groups.

Masarygus palmipalpus sp. n. is considered related to Masarygus planifrons because of the following shared characters: male basoflagellomere multifurcate; base of antenna in lateral view placed above dorsal eye margin; head strongly flattened; face concave; oral opening absent; abdomen dorsoventrally flattened; gradually widening hindward, with widest point at tergite 4; phallus furcate near apex, with both processes equally long.

In addition to Masarygus planifrons and Masarygus palmipalpus, two undescribed species are considered to belong to this genus. These species are included in the phylogenetic analyses of Reemer and Ståhls (in press) under the names Masarygus sp. 1 and sp. 2. The latter has three branches on the basoflagellomere, the first approximately 14. Whereas sp. 1 is placed in the same clade as Masarygus planifrons and Masarygus palmipalpus by Reemer and Ståhls (in press) (based on adult morphology), sp. 2 is placed in the clade containing Schizoceratomyia and Carreramyia. Species 2 is nevertheless included in Masarygus, because of the following characters: basoflagellomere multifurcate and bare (instead of bifurcate and pilose as in Schizoceratomyia); arista absent (present in Schizoceratomyia); base of antenna inserted on head above dorsal eye margin (not below as in Schizoceratomyia); vertex not strongly produced (in contrast with Carreramyia); crossvein r-m located within basal 1/10 of cell dm (between basal 1/4 and 1/8 in Schizoceratomyia); hind tibia not swollen and without long, brush-like pile (in contrast with Carreramyia). Unfortunately, the genitalia of the only known specimen of Masarygus species 2 are lost: there is a microvial containing postabdominal segments attached to the pin, but there are no genitalia in it.

Diversity and distribution.

Described species: 2. Neotropical. At least two undescribed species are known to occur (see Discussion). All species known so far, including the undescribed ones, have only been collected on one occasion.

Megodon Keiser (subgenus, see Microdon)
Type species:

Microdon falcatus Williston, 1887: 9. Type locality: Mexico.

Description.

Body length: 5–10 mm. Small, broadly built flies with long antennae and short, almost round abdomen. Head about as wide as thorax. Face convex; slighly narrower to slightly wider than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male parallel, not converging at level of frons, with mutual distance 4 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, sickle-shaped; bare. Postpronotum pilose. Scutellum semicircular; with small calcars or only with pair of small tufts of black microtrichiae posteriorly. Anepisternum without sulcus; pilose on slightly less than dorsal half, bare on slightly more than ventral half. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/8 and 1/10 of cell dm. Abdomen approximately round, 1 to 1.2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus straight, furcate near apex, with both processes about equally long; hypandrium without apical part; epandrium without ventrolateral ridge; surstylus furcate, with anterior lobe small and narrow, posterior lobe larger and wider.

Diagnosis.

Basoflagellomere sickle-shaped: curved upward. Anepisternum bare on ventral half. Cell r4+5 with postero-apical corner rectangular. Sternite 1 bare.

Discussion.

This is the only one known taxon among the Microdontinae in which the apical part of the hypandrium is entirely lacking (Fig. 156). Among the Neotropical taxa, this taxon is unique in the sickle-shaped basoflagellomere. The latter character also occurs to some extent in some Nearctic (Microdon adventitus, Microdon globosus)and Old World taxa (some Archimicrodon, Myiacerapis, Oligeriops Hul, 1937), but these differ from Menidon in several other important characters, such as a furcate phallus (unfurcate in Oligeriops) and absence of apical part of hypandrium (present in all other Microdontinae). These morphological singularities, combined with the phylogenetic results of Reemer and Ståhls (in press) (sister of (Piruwa + Paramicrodon)), are reasons to place Microdon falcatus in its own genus. Thompson (2007) clarified the taxonomy of the type species, which has several synonyms.

Diversity and distribution.

Described species: 1. Central and South America. Unpublished molecular evidence suggests that more than one species is involved, but this needs further study.

Etymology.

The generic name is a combination of the Greek words mene (moon) and odon, with the latter used as a suffix derived from Microdon. The prefix meni- was chosen because of the crescent-shaped basoflagellomere in the type species.

Type species:

Mermerizon inbio spec. n. Type locality: Costa Rica.

Description.

Stingless bee mimicking flies with moderately long antennae and elongate oval abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male parallel, not converging at level of frons, with mutual distance 3–4 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than (may be almost as long as) distance between antennal fossa and anterior oral margin; basoflagellomere slightly shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum without sulcus; pilose on dorsal half, bare on ventral half. Anepimeron pilose on dorsal half, bare on ventral half. Katepimeron convex; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located around basal 1/10 of cell dm. Abdomen oval, 2 to 3 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus slightly bent dorsad, furcate near apex, with dorsal process at least twice as long as ventral process; hypandrium with bulb-like base; epandrium without ventrolateral ridge.

Diagnosis.

Vein R4+5 with posterior appendix. Postero-apical corner of cell r4+5 rectangular, with small appendix. Postpronotum pilose. Propleuron bare. Membrane between sternites 2 and 3 less wide than sternite 2. Abdomen oval. Anepisternum bare on ventral half, pilose on dorsal half, except for small median bare part on dorsal half. Anepimeron bare on ventral half. (Male: eye margins parallel at level of frons, not converging).

Discussion.

The species of this genus are obvious mimics of stingless, Trigona-like bees in their tawny colouration and long pilose hind tibiae. At first sight they may be confused with Hypselosyrphus, Rhoga, or Stipomorhpa. From the first two genera, Mermerizon can be distinguished by the presence of a posterior appendix on vein R4+5, from Stipomorpha by the absence of a wide membrane between sternites 2 and 3. A presently undescribed Argentinian species lacks the long pilosity of the hind tibiae and does not seem to mimic these bees. Instead, it resembles Paragodon Thompson, 1969 and Surimyia Reemer, 2008 in general habitus, but is easily told apart by the presence of a posterior appendix on vein R4+5 and the male genitalia, which are very similar to those of the other two Mermerizon species.

Diversity and distribution.

Described species: 1. Descriptions of two additional species are in preparation by the first author. Neotropical (presently known from Costa Rica and Argentina).

Etymology.

The generic name is derived from the ancient Greek verb mermerizo, meaning ‘to deliberate’ or ‘to ponder’. This name was chosen because it took some deliberation before making the decision that a new genus was to be erected for the involved species. The name is to be treated as masculine.

Type species:

Microdon wulpii Mik, 1899: 143. Type locality: Indonesia, Sumatra. Replacement name for Microdon apicalis Wulp, 1892: 29 (preoccupied by Walker, 1858).

Description.

Body length: 7–21 mm. Slender to moderately broadly built flies with oval abdomen and long antennae. Head slightly wider than thorax. Face almost straight to convex in profile; narrower to wider than an eye. Lateral oral margins produced or not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male converging at level of frons, with mutual distance 2-3 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter than scape; bare. Postpronotum pilose. Scutellum semicircular; with or without calcars. Anepisternum sulcate; entirely pilose, except sometimes with small bare part ventrally (only known exception: Metadon bifasciatus, in which anepisternum is bare on entire ventral half). Anepimeron entirely pilose. Katepimeron flat to somewhat convex; smooth or with wrinkled texture; not pilose, but often with rows of microtrichia. Katatergum with oblique rows of microtrichia. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 angular to widely rounded, with or without appendix; crossvein r-m located between basal 1/7 and 1/4 of cell dm. Abdomen oval, 1.5-2.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus projecting not or little beyond apex of hypandrium (except projecting well beyond apex of hypandrium in Metadon bifasciatus), bent dorsad, furcate in apical half, with both processes about equally long (except ventral process much longer in Metadon bifasciatus); epandrium with or without ventrolateral ridge; surstylus unfurcate, sometimes with long posterior process.

Diagnosis.

Body never metallic green or blue. Vein R4+5 with posterior appendix. Abdomen oval, longer than wide but less than 2.5 times as long as wide. Postpronotum pilose. Anepisternum with bare part limited to ventral half, or entirely pilose. Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere shorter than or as long as scape. Tergite 1 short: length/width ratio 1:25 or less.

Discussion.

All included species (except the ones here described) were originally described in the genus Microdon. However, the morphology of Metadon is distinct. Characters that separate these taxa in all examined species (except Metadon bifasciatus, see below) are: anepisternum (almost) entirely pilose; phallus projecting not or only little beyond apex of hypandrium; aedegus furcate in apical half. Additional characters for distinguishing Metadon from Microdon (that may not work for all species) are: katepimeron more or less flat, with wrinkled texture; katatergum with oblique rows of microtrichia. In general, the abdomen of Metadon species is more elongate than that of Microdon species.

The East Palaearctic species Metadon bifasciatus Matsumura, 1916 is aberrant in certain characters. In this species the bare part of the anepisternum reaches up to about half the height of the sclerite. In addition, the genitalia are aberrant as the ventral aedeagal process is much longer than the dorsal process (Fig. 172), a character not known from any other species of Microdontinae. Nevertheless, this species is placed in Metadon because of the elongate abdomen and the oblique rows of microtrichia on the katatergum. This is supported by the results of Reemer and Ståhls (in press). As the Chinese species Microdon brunneipennis Huo, Ren & Zheng, 2007 and Microdon pingliensis Huo, Ren & Zheng, 2007 and Microdon spuribifasciatus Huo, Ren & Zheng, 2007 are similar to Microdon bifasciatus, the characters as mentioned may also be valid for those species.

Metadon is erected as a new genus distinct from Microdon in order to facilitate distinction between these apparently monophyletic groups. Results of phylogenetic analyses by Reemer and Ståhls (in press) support this decision.

Diversity and distribution.

Described species: 42. About half of the species (22) are described from the Oriental region. Several undescribed species from this region were seen by the first author in different collections. From the Afrotropical region, 14 species are described, remarkably none of which is from Madagascar. Four species are known from the Palaearctic region. These seem to form a closely related species group, all related to Microdon bifasciatus, restricted to eastern China, Korea and Japan. Two species are known from the Aru Islands off the southwest coast of New Guinea (these were collected by Alfred Russel Wallace in 1857, to be described by Walker 1858). These are the only known records of this group from the Australian region.

Etymology.

The generic name is a combination of the ancient Greek words meta and odon, with the latter used as a suffix derived from Microdon. The prefix meta is used in the sense of ‘near’ or ‘close’, in order to indicate the resemblance in habitus to Microdon s.s. It is a masculine name.


Microdon Meigen

Figs 176–240


Microdon Meigen, 1803: 275. Type species: Musca mutabilis Linnaeus, 1758: 592, by monotypy.

Aphritis Latreille, 1804: 193. Type species: Aphritis auropupescens Latreille, 1805, by subsequent monotypy. See Cheng and Thompson (2008) for synonymy.

Colacis Gistel, 1848: x. New name for Microdon Meigen. See Cheng and Thompson (2008) for synonymy.

Scutelligera Spix, 1824: 148. Type species: Scutelligera ammerlandia Spix, 1824: 124, by monotypy. See Cheng and Thompson (2008) for synonymy.

Parmula Heyden, 1825: 589. Type species: Parmula cocciformis Heyden, 1825: 589, by monotypy. See Cheng and Thompson (2008) for synonymy.

Scutigerella Haas, 1924: 148. Misspelling of Scutelligera Spix, 1824. See Cheng and Thompson (2008) for synonymy.


Subgenera (see separate accounts below)

Chymophila Macquart, 1834

Dimeraspis Newman, 1838 (= Mesophila Walker, 1849, syn. n.)

Megodon Keiser, 1971

Microdon s.s.

Myiacerapis Hull, 1949

Syrphipogon Hull, 1937


Species groups (see under Microdon s.l., after subgenera)

craigheadii-group

erythros-group

mirabilis-group

tarsalis-group

virgo-group


Unplaced species (see under Microdon s.l., after subgenera)

Microdon amabilis Ferguson, 1926

Microdon carbonarius Brunetti, 1923

Microdon macquariensis Ferguson, 1926

Microdon nigromarginalis Curran & Bryan, 1926

Microdon pagdeni Curran, 1942

Microdon pictipennis (Macquart, 1850)

Microdon rieki Paramonov, 1957

Microdon trimacula Curran, 1928

Microdon tsara Keiser, 1971

Microdon unicolor Brunetti, 1915

Microdon waterhousei Ferguson, 1926

Subgenus Chymophila Macquart Figs 176–180
Chymophila Macquart, 1834: 485. Type species: Chymophila splendens Macquart, 1834: 486, by monotypy.
Chimophila Osten Sacken, 1875: 46. Misspelling.
Eumicrodon Curran, 1925a: 50. Type species: Microdon fulgens Wiedemann, 1830: 82, by original designation. See Cheng and Thompson (2008) for synonymy.
Description.

Body length: 10–16 mm. Broadly built flies with oval to round abdomen and long antennae. Head about as wide as to slightly narrower than thorax. Face convex in profile; slightly narrower to slightly wider than an eye. Lateral oral margins produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare or very short pilose. Eye margins in male converging at level of frons, with mutual distance 1-3 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter than scape; bare. Postpronotum pilose. Scutellum trapezoid; with calcars. Propleuron pilose. Anepisternum with sulcus; pilose anterodorsally and posteriorly, extensively bare ventrally and medially. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Katatergum uniformly microtrichose. Wing: vein R4+5 with posterior appendix; vein M1 with outward angle, often with outward appendix, anteriorly recurrent; postero-apical corner of cell r4+5 widely rounded, with or without appendix; crossvein r-m located between basal 1/5 and 1/3 of cell dm. Abdomen oval, 1-1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus projecting far beyond apex of hypandrium, bent dorsad, furcate basally, with both processes equally long and very slender; epandrium with ventrolateral ridge; surstylus with two wide lobes; subepandrial sclerite with elongate anterior projection projecting well beyond surstylus in lateral view.

Diagnosis.

Vein R4+5 with posterior appendix. Abdomen oval. Vein M1 of characteristic shape: with outward angle, usually with small outward appendix, anteriorly recurrent (Fig. 177). In addition to this character, this subgenus also differs from Microdon s.s. in the aedeagal processes being longer and more slender, and in the subepandrial sclerite projecting anteriorly well beyond the surstylus in lateral view (Fig 178–180).

Discussion.

Species of this group are similar in overall habitus to Microdon s.s. Many species have metallic colours, but some are dull black or have a ‘tiger-striped’ abdomen. Previously, this group was considered to be exclusively Neotropical (Cheng and Thompson 2008). However, several Oriental and one Japanese species are very similar to the Neotropical species in both external characters and morphology of the male genitalia.

Diversity and distribution.

Described species: 34. Neotropical (25 species), Oriental (7 species), Nearctic (1 species) and Eastern Palaearctic (1 species from southern Japan).

Subgenus Dimeraspis Newman Figs 181–186
Dimeraspis Newman, 1838: 372. Type species: Dimeraspis podagra Newman, 1838, by monotypy.
Mesophila Walker, 1849: 1157. Type species: Ceratophya fuscipennis Macquart, 1834, by monotypy. Syn. n.
Description.

Body length: 8–12 mm. Broadly built flies with oval to round abdomen and long antennae. Head narrower than to about as wide as thorax. Face convex in profile; narrower to wider than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened or narrow (only in Microdon abditus Thompson, 1981). Eye bare. Eye margins in male converging at level of frons, sometimes only weakly so (Microdon adventitius Thompson, 1981, Microdon fuscipennis (Macquart, 1834)) with mutual distance 2-5 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than or as long as distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape; bare. Postpronotum pilose. Scutellum semicircular to trapezoid; without calcars, but large and blunt calcars may seem to be present due to strong apicomedian sulcus. Propleuron bare. Anepisternum without sulcus (or only a very weak one dorsally); pilose dorsally, extensively bare on slightly more or slighly less than ventral half. Anepimeron entirely pilose. Katepimeron more or less convex; smooth or with wrinkled texture (Microdon fuscipennis); bare. Katatergum uniformly microtrichose. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5, slightly recurrent; postero-apical corner of cell r4+5 rectangular, with appendix; crossvein r-m located between basal 1/7 and 1/4 of cell dm. Abdomen oval, 1-1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus projecting little beyond apex of hypandrium, bent dorsad, furcate apically, with both processes equally long; epandrium with ventrolateral ridge; surstylus with wide basal lobe and narrow posterior lobe.

Diagnosis.

Difficult to diagnose, because included species vary strongly in several key characters. See key and discussion.

Discussion.

This group was erected for the Nearctic Dimeraspis podagra Newman, 1838, a subjective synonym of Mulio globosus Fabricius, 1805 (Thompson 1981b). This species differs from Microdon s.s. in the unsulcate anepisternum, the bare propleuron, the rectangular postero-apical corner of cell r4+5, and the male genitalia: phallus apically furcate, hypandrium with bulb-like base. Some other Nearctic (and one Cuban) species are very similar in morphology of the male genitalia: Microdon abditus Thompson, 1981, Microdon adventitius Thompson, 1981, Microdon fuscipennis (Macquart, 1834), Microdon marmoratus Bigot, 1883, and Microdon remotus Knab, 1917. Thompson (1981b) also regarded these species as related, with the ‘globosus complex’ (Microdon abditus, Microdon globosus, Microdon marmoratus) as sister to the fuscipennis-group (Microdon adventitius, Microdon fuscipennis, Microdon remotus). These species are also similar in their overall brownish colouration and in the wing venation. The morphological similarities are here taken as a reason to include all species in Dimeraspis. Because of similarities in male genitalia this group might tentatively be considered related to Archimicrodon, Menidon or Serichlamys. However, because of considerable uncertainty, the group is here treated as a subgenus of Microdon.

Mesophila Walker, 1849 was erected for Ceratophya fuscipennis Macquart. As this species is here included in the older genus group Dimeraspis, Mesophila becomes a junior synonym of Dimeraspis.

Diversity and distribution.

Described species: 5. Nearctic (4 species) and West Indian (1 species from Cuba).

Subgenus Megodon Keiser Figs 187–195
Megodon Keiser, 1971: 252. Type species: Megodon stuckenbergi Keiser, 1971: 253, by original designation.
Description.

Body length: 8–13 mm. Broadly built flies with oval abdomen and long antennae. Head about as wide as thorax. Face convex in profile; narrower than an eye. Lateral oral margins slightly produced. Vertex flat. Occiput narrow and parallel-sided over entire length. Eye bare. Eye margins in male converging at level of frons, with mutual distance about equal to width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter than to as long as scape; bare. Postpronotum pilose. Scutellum trapezoid; with strongly developed calcars. Anepisternum weakly sulcate; pilose anterodorsally and along posterior margin, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 angular to weakly rounded, with or without appendix; crossvein r-m located around basal 1/6 of cell dm. Abdomen oval, around 1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus furcate near base, with processes equally long and projecting well beyond apex of hypandrium; epandrium with ventrolateral ridge; surstylus unfurcate, elongate, curved dorsad.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum pilose. Abdomen oval. Anepisternum widely bare medially. Propleuron bare. Postero-apical corner of cell r4+5 more or less rectangular. Antenna longer than distance between antennal fossa and anterior oral margin. Occiput narrow and parallel-sided over entire length (not widened dorsally). First tarsomere of hind leg dorsally with wide longitudinal groove.

Discussion.

Keiser (1971) erected this genus to include a species with very large, cone-shaped scutellar calcars. Cheng and Thompson (2008) did not study this species and refrained from commenting on the status of the group. The first author was able to study the holotype of Megodon stuckenbergi Keiser, 1971, as well as some additional material.

Megodon is very similar in external morphology to Microdon. Their genitalia also share important characters, like the deeply furcate phallus, the long aedeagal processes and the presence of a ventrolateral ridge on the epandrium. There are also differences, most notably the entirely narrow and parallel-sided occiput, and the dorsal, longitudinal groove on the first tarsomere of the hind leg. The shared characters are here considered more important than the differences. Because of these considerations, combined with the phylogenetic results of Reemer and Ståhls (in press), Megodon is here treated as a subgenus of Microdon.

Microdon planitarsus Keiser, 1971 is here also assigned to Megodon, because it agrees with the diagnostic characters as described above, and its male genitalia are very similar to those of Microdon stuckenbergi (Figs 193, 195). In Microdon planitarsis, the scutellar calcars are not as large and cone-shaped as in Microdon stuckenbergi. This indicates that the size and shape of these calcars should not be regarded as group-defining.

Diversity and distribution.

Described species: 2. Madagascar. One undescribed species from Madagascar is known to the first author.

Subgenus Microdon Meigen, s.s. Figs 196 –214
Description.

Body length: 7–14 mm. Broadly built flies with oval abdomen and long antennae. Head narrower to slightly wider than thorax. Face convex in profile; slightly narrower to wider than an eye. Lateral oral margins not or weakly produced. Vertex flat. Occiput ventrally narrow to wide, dorsally widened. Eye bare. Eye margins in male converging at level of frons, with mutual distance 2-4 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape; bare. Postpronotum pilose. Scutellum semicircular to trapezoid; with or without calcars. Propleuron pilose. Anepisternum sulcate; pilose anterodorsally and posteriorly, widely bare ventrally and medially. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Katatergum uniformly microtrichose. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5, sometimes with slight inward angle in anterior 1/3; postero-apical corner of cell r4+5 rounded, with or without appendix; crossvein r-m located between basal 1/6 and 1/4 of cell dm. Abdomen oval, 1-1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus projecting clearly beyond apex of hypandrium, bent dorsad, furcate close to base, with both processes about equally long or dorsal process longer than ventral process; epandrium with ventrolateral ridge; surstylus with two short, wide lobes.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum pilose. Abdomen oval. Anepisternum extensively bare ventrally and medially. Postero-apical corner of cell r4+5 rounded. Katepimeron convex, without microtrichia. Apical crossvein M1 without outward angle. Lateral oral margins not or weakly produced.

Discussion.

As Cheng and Thompson (2008) wrote, this genus has remained “somewhat a catch all for various unrelated species not placed in other genera”. Many species previously placed inMicrodon are transferred to other genera in the present paper, e.g. Archimicrodon, Metadon and Peradon. These classificatory changes are supported by the results of the phylogenetic analysis of combined molecular and morphological characters by Reemer and Ståhls (in press). The analysis of only morphological characters by Reemer and Ståhls (in press) included many additional species which do not obviously belong to any of the previously recognized genus groups, nor to the genera erected in the present paper. The phylogenetic results offer little or no clues as to their taxonomic affinities. As most of these species were originally described in Microdon, and were subsequently maintained in that genus, the pragmatic solution is here chosen to keep these taxa in Microdon s.l. (see below). This category should not be confused with the supposedly monophyletic Microdon s.s. as defined above, as Microdon s.l. is probably not monophyletic. For some of these taxa, genus group names are available, which are here treated as subgenera (see separate accounts). The other taxa are here placed in species groups or left unplaced. These taxa are discussed below.

Unlike the other species groups discussed below, the virgo species group is considered to belong within Microdon s.s.

Diversity and distribution.

Described species: 62. Occurs in Nearctic (13 species), Neotropical (14), Oriental (9) and Palaearctic (26) regions.

Subgenus Myiacerapis Hull Figs 215–220
Myiacerapis Hull, 1949: 309. Type species: Microdon villosus Bezzi, 1915: 135, by original designation.
Description.

Body length: 12 mm. Broadly built flies with bee-like pilosity and long antennae. Head wider than thorax. Face convex; wider than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare or very short and sparsely pilose. Eye margins in male hardly converging at level of frons, with mutual distance about 5 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum weakly sulcate; pilose anteriorly and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 slightly recurrent, but more or less perpendicular to vein R4+5; postero-apical corner of cell r4+5 rounded, without appendix; crossvein r-m located around basal 1/4 of cell dm. Abdomen oval, about 1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus furcate, with furcation point near base; epandrium with ventrolateral ridge; surstylus unfurcate.

Diagnosis.

Abdomen oval, about 1.5 times as long as wide. Vein R4+5 with posterior appendix. Postpronotum pilose. Proepimeron bare. Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere longer than scape. Anepisternum with bare ventromedian part extending to dorsal half. Sternite 1 pilose. Scutellum without calcars.

Discussion.

Myiacerapis was described as a subgenus of Microdon. In morphology it is quite similar to Microdon s.s. as defined in the present paper, also in the male genitalia (deeply furcate phallus with equally long processes, epandrium with ventrolateral ridge). However, unlike Microdon s.s. it has a bare proepimeron (pilose in Microdon s.s.) and a wrinkled texture of the katepimeron. Therefore, it is not placed in Microdon s.s. here, but in Microdon s.l, in awaitance of better understanding of its phylogenetic affinities.

Diversity and distribution.

Described species: 1. Africa (Uganda). An undescribed species is known from South Africa (coll. BMNH).

Subgenus Syrphipogon Hull Figs 221–222
Syrphipogon Hull, 1937b: 120. Type species: Syrphipogon fucatissimus Hull, 1937: 120, by original designation.
Description.

Body length: 25–28 mm. Very large flies with oval abdomen and long, colourful pilosity. Mimics of orchid bees of the genus Eulaema (Euglossidae). Head about as wide as thorax. Face more or less straight in profile; narrower than an eye; on ventral half with very long, thick and dense pile, resembling a beard (‘mystax’). Eye margins in male converging at level of frons, with mutual distance about twice as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter than scape, oval, about four times as long as wide, bare. Postpronotum bare. Scutellum trapezoid; with very large, cone-shaped calcars. Anepisternum sulcate; pilose anterodorsally and posteriorly, widely bare medially. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Wing: vein R4+5 with posterior appendix; vein M1 straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded, without appendix; crossvein r-m located around basal 2/7 of cell dm. Abdomen oval, about 1.3 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus furcate, with furcation point near base, both processes about equally long, curved dorsad, projecting well beyond apex of hypandrium; epandrium without ventrolateral ridge; surstylus shallowly furcate, with two short and wide lobes.

Diagnosis.

Body length more than 20 mm. Face with very long, thick and dense pile, resembling a beard (‘mystax’).

Discussion.

Hull (1937b) erected Syrphipogon, and considered it related to Microdon. Steyskal (1953) referred to Hull’s description in his own description of an apparently very similar species (Microdon gaigei Steyskal, 1953), but he considered the differences with Microdon insufficient for generic status. In external characters and male genitalia Microdon and Syrphipogon are quite similar. For that reason, Syrphipogon is here still treated as a subgenus of Microdon.

The differences between the two species of Syrphipogon are not very convincing when comparing the description of Steyskal (1953), based on a female, with the holotype of Syrphipogon fucatissimus Hull, 1937, a male. The differences as noted by Steyskal (1953) may be due to sexual dimorphism, but in order to establish this, the type of Microdon gaigei needs to be examined.

Diversity and distribution.

Described species: 2. Neotropical. Only two specimens are known: one from Panama and one from “South America”.


Microdon s.l. (species groups and unplaced species)

craigheadii-group.

Only one species is included in this group: Microdon craigheadii Walton, 1912. This slender, metallic green Nearctic species is similar in habitus to Laetodon and many species of Microdon s.l. From these groups, Microdon craigheadii differs in the structure of the basal part of the phallus: the part of the phallus connecting the basal spherical part with the apical part is complexly curved (Fig. 232). This is a very unusual structure in Microdontinae, only found in this species and in Kryptopyga. In other genitalic structures (phallus deeply furcate, epandrium with ventrolateral ridge) as well in external morphology, Microdon craigheadii is very similar to Microdon s.s. Because of the peculiar morphology of the genitalia, the species is placed in a separate species group within Microdon s.l.

erythros-group.

In overall habitus and many external characters, the species of this group remind of both Microdon s.s. and Metadon. Placement in Microdon s.s. is contradicted by the phallus being furcate apically (Fig. 233), whereas placement in Metadon is contradicted by the extensively bare anepisternum. As the phylogenetic analysis of morphological characters (Reemer and Ståhls in press) provides no information on the affinities of Microdon erythros Bezzi, 1908, this species is placed in Microdon s.l., along with the similar Microdon luteiventris Bezzi, 1915.

mirabilis-group.

The species of this Neotropical group have contrasting yellow and black colour patterns on the wings, combined with remarkably long hind legs, evoking a resemblance to certain Pompilidae (Hymenoptera). Apart from this, they differ from Microdon s.s. in the bare propleuron and the aedeagal processes projecting hardly beyond the apex of the hypandrium.

Apart from Microdon mirabilis, this group includes Microdon bertonii Bezzi, 1910 (= Microdon arcuatus Curran, 1941, syn. n.) and Microdon iheringi Bezzi, 1910. The species seem to differ only in colouration of wings, legs and abdomen. However, quick glances in museum collections (e.g. USNM) suggest that intermediate specimens exist. This indicates that species taxonomy of this group needs further attention.

Bezzi (1910) wrote that he had two male specimens Microdon iheringi in his collection, which he both considered as ‘cotypes’. The collection of the MCSN (Milan) presently holds only one specimen (a male), which was examined by the first author. It is uncertain whether the other specimen still exists. In order to assure stability of this taxon, the specimen in the MCSN-collection is here designated as lectotype. Label information is as follows: label 1: “5695”; label 2: “S. Paulo / Brasile / 26.X.06 / Hering”; label 3: “iheringi”; label 4 (red): “LECTOTYPE / Microdon iheringi / Bezzi, 1910 / Des. M. Reemer 2009”.

tarsalis-group.

This group only includes the Afrotropical species Microdon tarsalis Hervé-Bazin, 1913 and its synonym Microdon bequaerti Curran, 1929 (syn. n.). In the phylogenetic analysis of morphological characters (Reemer and Ståhls in press) this species was recovered in the Microdon s.l. clade, but its exact relationship with the other groups in this clade were unresolved. This group differs from Microdon s.l. in e.g. the entirely narrow occiput, the short and characteristically shaped phallus with the dorsal process longer than the ventral process, and the absence of a ventrolateral ridge on the epandrium. Besides, there is a patch of pile with hook-shaped apexes on the hind basitarsus dorsally on its inner surface.

In overall habitus (including swollen hind basitarsus), Microdon tarsalis is remarkably similar to the Nearctic Microdon (Dimeraspis) abditus Thompson, 1981 but considering the differences in male genitalia this similarity is probably merely superficial. These differences are: phallus with dorsal process longer than ventral process (equally long in Microdon abditus), epandrium without ventrolateral ridge (with ventrolateral ridge in Microdon abditus), surstylus simple shaped, without distinct posterior process (with posterior process in Microdon abditus).

virgo-group.

This group consists of Neotropical metallic green, blue or bronze flies, sometimes partly reddish. It is differentiated from Microdon s.s. in the key by the bare propleuron and the strongly produced lateral oral margins, of which the anterolateral corners are distinctly angular (Fig. 229). The latter character is presented with some hesitation, as it is uncertain whether it works for all species. Possibly, certain species here placed in Microdon s.s. also belong in this group. Therefore, the virgo-group is here considered as a species group within Microdon s.s., instead of within Microdon s.l. As it is presently uncertain which species should be assigned to it, this group is not recognized in the species catalogue in this paper.

Unplaced species.

Several species of Microdon s.l. (see Appendix 2) do not fit into any of the groups described above. In the phylogenetic analyses of Reemer and Ståhls (in press), the following species belonging to this group were included: Microdon amabilis Ferguson, 1926, Microdon carbonarius Brunetti, 1923, Microdon nigromarginalis Curran & Bryan, 1926, Microdon pictipennis (Macquart, 1850), Microdon rieki Paramonov, 1957, Microdon trimacula Curran, 1928, Microdon tsara Keiser, 1971, Microdon waterhousei Ferguson, 1926. The results hardly offer solid clues as to their exact relationships with Microdon s.s. For examples of morphology of these species see Figs 230, 231, 237–240.

Diversity and distribution.

In total, 126 species (from all continents except Antarctica) are here classified under Microdon. Of these, 62 are placed in Microdon s.s., 46 in other subgenera, and 18 are not placed in subgenera (although some of them in species groups) but left in Microdon s.l.

Mixogaster Macquart

http://species-id.net/wiki/Mixogaster

Figs 241–248
Mixogaster Macquart, 1842: 14. Type species: Mixogaster conopsoides Macquart, 1872: 14, by original designation.
Myxogaster Kertész, 1910: 351. Misspelling.
Myxogaster Shiraki, 1930: 8. Misspelling.
Description.

Body length: 9–15 mm. Slender flies with constricted abdomen, wasp-like. Head wider than thorax. Face convex or almost straight in profile; about as wide as an eye or narrower. Lateral oral margins not produced. Vertex flat. Occiput narrow, except slightly widened dorsally. Eye bare. Eyes in male not or hardly converging at level of frons, with mutual distance 4 to 5 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer or shorter than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum with weak sulcus; entirely bare or pilose anterodorsally, or pilose anterodorsally and along posterodorsal margin. Anepimeron entirely pilose or bare on ventral half. Katepimeron convex; bare. Wing vein R4+5 without posterior appendix. Vein M with small anterior appendix into cell r4+5. Vein M1 either straight or with anterior part directed outward, with one or two angles, whether or not with small inward appendix and /or small outward appendix. Postero-apical corner of cell r4+5 angular. Crossvein r-m located betwee basal 1/4 to 2/5 of cell dm. Abdomen constricted at base, with tergite 2 varying in length and width. Tergites 3 and 4 not fused. Male genitalia: phallus unfurcate, bent dorsad, with either lateral or dorsal combined with ventral lamellae, sometimes with apical spines; hypandrium with bulb-like base and apical part consisting of separate lobes, or hypandrium entirely consisting of two separate parts, which are not interconnected; epandrium without ventrolateral ridge; surstylus of varying shape.

Diagnosis.

Vein M with small anterior appendix into cell r4+5. Abdomen constricted. Metapleura connected, postmetacoxal bridge complete.

Discussion.

An important diagnostic character of Mixogaster, the anterior appendix of vein M, is also found in Spheginobaccha de Meijere, 1908 and certain specimens of Aristosyrphus primus. These taxa also share the character of the apical part of the hypandrium consisting of two separate lobes. See genus account of Aristosyrphus for discussion.

The morphology of the male genitalia is remarkably diverse in this genus, much more so than in other groups of Microdontinae (except perhaps Aristosyrphus / Eurypterosyrphus). Some species have characters not known from any other Microdontinae. Some examples are illustrated in Figs 245–248. In Mixogaster breviventris Kahl, 1897, the phallus has wide dorsal and ventral lamellae (Fig. 245). This type of genitalia is found in all Nearctic species, which also have a straight vein M1 in common. In Microdon thecla Hull, 1954 (Fig. 247), the hypandrium consists of two separate lobes, which are not interconnected ventrally to envelope the phallus, as is the case in all other studied Microdontinae. Besides, the subepandrial sclerite is strongly developed in this species, and produced well beyond the epandrium in lateral view. In an undescribed species (Fig. 248), the phallus is asymmetric in ventral view, with wide lateral lamellae, which are apically densely occupied with irregular spines. This is the only known case of asymmetric genitalia among Microdontinae. The spinose phallus is also a unique character.

The keys to the species by Hull (1954) and Carrera and Lenko (1958) (Brazilian species only) work reasonably well, but the existence of several undescribed species makes it necessary to check original descriptions or, preferably, type material in order to verify identifications. Considering the large interspecific variation in the male genitalia, these characters should be further explored in future (re)descriptions of species.

Diversity and distribution.

Described species: 21. Mainly Neotropical, with three species in the Nearctic. At least one Nearctic and several Neotropical species are undescribed.


Myiacerapis Hull (subgenus, see Microdon)
Oligeriops Hull

http://species-id.net/wiki/Oligeriops

Figs 249–253
Oligeriops Hull, 1937a: 26. Type species: Microdon chalybeus Ferguson, 1926a: 176, by original designation.
Description.

Body length: 7–10 mm. Dark-coloured, stout-legged flies with oval abdomen and moderately long antennae. Head about as wide as thorax. Face convex; wider than an eye. Lateral oral margins produced. Vertex flat. Occiput wide over entire length, narrowest point halfway. Eye bare. Eye margins in male not converging at level of frons, with mutual distance around 4 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape; with dorsal margin curved dorsad, more or less sickle-shaped; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum weakly sulcate; pilose, with small bare part on ventral half. Anepimeron entirely pilose. Katepimeron convex; with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located between basal 1/6 of cell dm. Abdomen oval, about twice as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus not or little projecting beyond apex of hypandrium, slightly bent dorsad, shallowly furcate, with both processes about equally long; epandrium without ventrolateral ridge; surstylus unfurcate.

Diagnosis.

Vein R4+5 with posterior appendix. Postpronotum pilose. Abdomen oval. Anepisternum largely pilose, at most with small bare part on ventral half. Basoflagellomere sickle-shaped: dorsal margin curved upward.

Discussion.

Hull (1937a) described Oligeriops as a genus, with only Microdon chalybeus Ferguson, 1926 included, without indicating its diagnostic generic characters. Hull (1949) used the reduced size of the eyes (due to widened occiput and gena) and the sickle-shaped antenna as key characters. Thompson and Vockeroth (1989) list Oligeriops as synonym of Microdon. Cheng and Thompson (2008) express their doubts about ranking Oligeriops as a genus, while referring to the antennae of Australian Microdon species as illustrated in Ferguson (1926b). These illustrations show that other species originally described in Microdon also have a curved basoflagellomere, just like Microdon chalybeus Ferguson, 1926, but nevertheless these species were not included in Oligeriops by Hull (1937a, 1949). Cheng and Thompson (2008) state that ‘Whether these other species have reduced eyes remains to be seen!’. However, as Ferguson (1926a, b) already noticed, the four species he described are all ‘close’ and ‘very similar’. Examination of type specimens, additional material and original descriptions, has confirmed this, and has made clear that all five species presently included in Oligeriops have reduced eyes and sickle-shaped basoflagellomeres indeed. Based on these and other morphological similarities, there is no doubt that they are closely related.

Oligeriops does not fit into the concept of Microdon s.s. as defined in the present paper. In addition to the reduced size of the eye and the curved basoflagellomere, the following characters distinguish Oligeriops from Microdon: anepisternum almost entirely pilose, at most with small bare part ventrally; propleuron bare; postero-apical corner of cell r4+5 rectangular; phallus projecting little beyond apex of hypandrium, furcate near apex. Considering these characters in combination with the results of Reemer and Ståhls (in press), it is deemed not appropriate to include this taxon in Microdon.

Diversity and distribution.

Described species: 5. Australia (incl. Tasmania).

Omegasyrphus Giglio-Tos, stat. n.

http://species-id.net/wiki/Omegasyrphus

Figs 254–256
Omegasyrphus Giglio-Tos, 1891: 4. Type species: Microdon coarctatus Loew, 1864: 74, by subsequent designation of Giglio-Tos (1892: 3).
Description.

Body length: 7–9 mm. Small, dark flies with relatively short antennae and characteristically shaped abdomen. Head slightly wider than thorax. Face convex; about as wide as or narrower than an eye. Lateral oral margins hardly produced. Vertex flat or slightly produced, densely pilose. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male slightly converging at level of frons, with mutual distance 2.5-3 times width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin; basoflagellomere as long as or longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; with calcars. Anepisternum sulcate; entirely pilose. Anepimeron entirely pilose. Katepimeron moderately convex; with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular to weakly rounded, with small appendix; crossvein r-m located between basal 1/6 to 1/5 of cell dm. Abdomen 2.5-3 times as long as wide; with characteristic shape: widest point about halfway tergite 2, which has strongly arcuate lateral margins and pair of depressed areas dorsally; tergites 3-4 narrower and almost parallel-sided. Tergites 3 and 4 fused. Sternite 1 pilose. Male genitalia: phallus furcate near apex, with dorsal process long and whip-like, ventral process very short; epandrium with ventrolateral ridge.

Diagnosis.

Vein R4+5 with posterior appendix. Antenna shorter than distance between antennal fossa and anterior oral margin. Tergite 2 with strongly arcuate lateral margins, tergites 3-4 narrower and almost parallel-sided. Sternite 2 and 3 separated by membrane that is much less wide than sternite 2.

Discussion.

This group was treated as a subgenus of Microdon by Thompson (1981b). Based on the phylogenetic evidence of Reemer and Ståhls (in press) this ranking cannot be maintained. Instead, Omegasyrphus is treated as a distinct genus. Thompson (1981b), who gives a key to the North American species, points out that species level taxonomy is necessary for this genus. This is still true.

Diversity and distribution.

Described species: 5. North and Central America, from South Dakota in the U.S.A. southward to Guatemala. The south border of this range is marked by Microdon brunnipennis Hull, 1944, which was described as a variety of Microdon baliopterus Loew, 1872 by Hull (1944b). The assignment of this taxon to Omegasyrphus is based only on this description, as the type has not been examined.

Paragodon Thompson

http://species-id.net/wiki/Paragodon

Figs 257–261
Paragodon Thompson, 1969: 74. Type species: Paragodon paragoides Thompson, 1969: 81, by original designation.
Description.

Body length: 4–5 mm. Small flies with short antennae and oval abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male not converging at level of frons, with mutual distance about three times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval, about 1.5 times as long as wide, bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum convex; pilose anteriorly and posterodorsally, widely bare in between. Anepimeron bare or with a few thick, seta-like pile dorsally. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located very close to base of cell dm. Abdomen oval, about 1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus unfurcate, straight, projecting only little beyond apex of hypandrium; hypandrium with bulb-like base; epandrium without ventrolateral ridge; surstylus unfurcate.

Diagnosis.

Abdomen oval; yellow and black. Vein R4+5 without posterior appendix. Crossvein r-m almost at same level as base of cell dm. Antenna shorter than distance between antennal fossa and anterior oral margin. Postpronotum pilose.

Discussion.

When Thompson (1969) described this genus, he stated that it appeared to be the most primitive microdontine fly known. This was based on a number of presumed plesiomorphic characters: 1) unsclerotized ejaculatory apodeme and sac; 2) short antenna; 3) underdeveloped and bare metasternum; 4) lack of basal setal patches on hind femur; 5) lack of a spurious vein; 6) lack of appendix on vein R4+5; 7) presence of a double sustentacular apodeme; 8) unfurcate phallus. Now that a larger number of taxa of Microdontinae could be studied, all of these characters were also found in other taxa (Reemer and Ståhls in press), except for the unsclerotized ejaculatory apodeme. See also discussion under Surimyia.

Diversity and distribution.

Described species: 1. Central America (Mexico, Costa Rica and Panama).

Paramicrodon de Meijere

http://species-id.net/wiki/Paramicrodon

Figs 262–268
Paramicrodon de Meijere, 1913: 359. Type species: Paramicrodon lorentzi Meijere, 1913: 360, by monotypy.
Syrphinella Hervé-Bazin, 1926: 73. Type species: Syrphinella miranda Hervé-Bazin, 1926: 74, by monotypy.
Myxogasteroides Shiraki, 1930: 9. Type species: Myxogaster nigripennis Sack, 1922: 275, by original designation.
Nannomyrmecomyia Hull, 1945: 75. Type species: Paramicrodon delicatulus Hull, 1937: 24, by original designation. Described as subgenus of Spheginobaccha.
Description.

Body length: 4–11 mm. Small, slender flies with short antennae and more or less parallel-sided abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally strongly widened. Eye bare. Eye margins in male only slightly converging at level of frons, with mutual distance 1.5-2.5 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval, about 1.5 times as long as wide, bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum convex; pilose anteriorly and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located within basal 1/10 of cell dm. Abdomen elongate: more or less parallel-sided, may be subtly constricted at tergite 3 (male), or slightly oval (female); 2.5–4 times as long as wide. Tergites 3 and 4 fused (but distinct suture visible). Sternite 1 bare or pilose. Sternites 3-4 strongly narrowed; narrower than sternite 2, with wide membraneous parts laterally. Male genitalia: phallus furcate near apex, slightly bent dorsad, projecting well beyond apex of hypandrium; hypandrium with apical part consisting of two separate lobes; epandrium without ventrolateral ridge; surstylus of varying shape.

Diagnosis.

Vein R4+5 without posterior appendix. Postpronotum pilose. Antenna shorter than distance between antennal fossa and anterior oral margin. Vein M1 straight, not parallel to wing margin, perpendicular to both vein R4+5 and M. Mesonotum with transverse suture incomplete. Sternites 3-4 strongly narrowed; narrower than sternite 2, with wide membraneous parts laterally.

Discussion.

The synonymy of Syrphinella Hervé-Bazin, 1926 with Paramicrodon was suspected by Hull (1937a) and stated explicitly by Hull (1949). This subjective synonymy is here confirmed, based on examination of the type specimen of the type species. Myxogasteroides Shiraki, 1930 was treated as a synonym of Paramicrodon by Hull (1949) and Cheng and Thompson (2008), a synonymy followed here based on the description of the type species. The synonymy of Nannomyrmecomyia Hull, 1945 and Paramicrodon was stated by Thompson (1969, 1981a) and is also confirmed here based on examination of the type specimens.

Diversity and distribution.

Described species: 8. The range of this genus is interestingly disjunct, with six species from the Oriental Region (Thailand to Moluccas), one from New Guinea and two from the Neotropical region. At least one additional species occurs in the Neotropical region (unpublished observations by the first author), but more species-level work is needed to sort this out.

Paramixogaster Brunetti

http://species-id.net/wiki/Paramixogaster

Figs 269–284
Paramixogaster Brunetti, 1923: 319. Type species: Paramixogaster vespiformis Brunetti, 1923: 320, by original designation.
Paramixogasteroides Shiraki, 1930: 8. Type species: Myxogaster variegata Sack, 1922: 16, by original designation.
Tanaopicera Hul, 1945: 76. Type species: Ceratophya variegatus Walker, 1852: 220, by original designation.
Description.

Body length: 5–13 mm. Slender flies with constricted abdomen and long antennae, usually with black and yellow colour pattern, wasp mimics. Head wider than thorax. Face convex in profile; narrower than to wider than an eye. Lateral oral margins not produced. Vertex flat to strongly swollen. Occiput ventrally narrow, dorsally widened. Antennal fossa about as wide as high. Eye bare. Eye margins in male parallel, not converging at level of frons. Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere usually much longer than scape, except shorter in Paramixogaster illucens (Bezzi) and Paramixogaster luxor Curran (see Discussion); bare. Postpronotum bare. Mesoscutum with transverse suture usually incomplete, except complete in Paramixogaster contractus, Paramixogaster conveniens and Paramixogaster omeanus (see Discussion). Scutellum semicircular; without or with small calcars. Anepisternum convex or sulcate; entirely pilose or partly bare on ventral half. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 with or without posterior appendix; vein M1 perpendicular to vein R4+5 and vein M; postero-apical corner of cell r4+5 rectangular to somewhat acute, with small appendix; crossvein r-m located within basal 1/4 of cell dm. Abdomen elongate, at least 3 times as long as wide; constricted, with narrowest point at tergite 2 and widest point at tergite 3 or 4. Tergites 3 and 4 fused. Male genitalia: phallus furcate, with furcation point in distal 1/3; epandrium without ventrolateral ridge; surstylus weakly furcate, only in Paramixogaster luxor consisting of three distinct branches.

Diagnosis.

Postpronotum bare. Basoflagellomere at least three times as long as wide. Posterio-apical corner of wing cell r4+5 rectangular or somewhat acute. Abdomen usually constricted (i.e. with narrowest point at tergite 2 and widest point at tergite 3 or 4); if not, then the following three characters apply: 1) basoflagellomere 2-4 times as long as scape, 2) tergite 2 less than half as long as tergites 3 and 4 together, 3) face smooth medially (without vitta of transversely wrinkled texture).

Discussion.

Cheng and Thompson (2008) regarded Paramixogasteroides Shiraki, 1930 and Tanaopicera Hull, 1945 as subjective synonyms of Paramixogaster. Examination of the type species of Tanaopicera, Ceratophya variegata Walker, 1852, confirmed this opinion with regard to Tanaopicera. One of the characters Hull (1945) used to characterize Tanaopicera was ‘the high, greatly developed vertex’. However, the vertex in the holotype of Ceratophya variegata is neither high nor greatly developed. This species is very similar to other Paramixogaster-species in all important characters. The type species of Paramixogasteroides, Myxogaster variegata Sack, was not examined, but its description by Sack (1922) is clear enough to include this taxon in Paramixogaster.

Morphological variation among the species presently included in Paramixogaster is large. Although most species have a constricted abdomen in dorsal view, this is not the case in the African taxa Paramixogaster acantholepidis (Speiser, 1913) and Paramixogaster crematogastri (Speiser, 1913), and the Australian species Paramixogaster praetermissus (Ferguson, 1926). However, tergite 2 is dorsoventrally flattened in these species, so in lateral view their abdomen appears constricted. In all other important characters of external morphology and male genitalia these taxa belong in Paramixogaster, as corroborated by the results of the phylogenetic analysis based on morphology (Reemer and Ståhls in press).

Paramixogaster illucens (Bezzi, 1915) and Paramixogaster luxor (Curran, 1931) are the only species included in this genus in which the basoflagellomere is shorter than the scape. In Paramixogaster luxor, the shape of the surstylus also differs from the other species, as it consists of three separate branches (Fig. 282). Nevertheless, both species are included in Paramixogaster because agree with the diagnosis.

Paramixogaster contractus (Brunetti, 1923), Paramixogaster conveniens (Brunetti, 1923) and Paramixogaster omeanus (Paramonov, 1957) are aberrant from all other known species of Paramixogaster in their complete transverse suture. This character is also found in Indascia, which includes species which look superficially similar to these Paramixogaster-species. However, these species are here assigned to Paramixogaster, based on the phylogenetic analysis of their morphology (Reemer and Ståhls in press). In addition, they possess a diagnostic character for Paramixogaster: the bare postpronotum. The first two species, Paramixogaster contractus and Paramixogaster conveniens, differ from all other studied species of Microdontinae in the presence of pile on the metaepisternum. It will be interesting to re-evaluate their taxonomic affinities when additional material becomes available. At present, the species are only known from the holotypes, which both are females, so no characters of male genitalia or DNA could be analyzed.

As a consequence of transferring some species from other genera to Paramixogaster, replacement names had to be chosen for two species. Examination of the type of Microdon vespiformis de Meijere, 1908 made clear that this is a species of Paramixogaster. As Mixogaster vespiformis Brunetti, 1913 was later designated as the type species of Paramixogaster, these two names are now secondary homonyms. For the junior name, vespiformis Brunetti, the nomen novum Paramixogaster brunettii is proposed here. The other new name introduced here is Paramixogaster sacki for Paramixogasteroides variegata Sack, 1922, which is a junior secondary homonym of Ceratophya variegata Walker, 1852.

Diversity and distribution.

Described species: 26. Afrotropical (5 species), Oriental (12) and Australian region (9). Several additional species, from all three regions, await description.

Parocyptamus Shiraki

http://species-id.net/wiki/Parocyptamus

Figs 285–290
Parocyptamus Shiraki, 1930: 11. Type species: Parocyptamus sonamii Shiraki, 1930: 12, by original designation.
Stenomicrodon Hull, 1937a: 26. Type species: Stenomicrodon purpureus Hull, 1937: 26, by original designation. See Hull (1949) for synonymy.
Description.

Body length: 11–15 mm. Slender flies with elongate, tapering abdomen and long antennae, black with metallic hues, wings infuscated. Head about as wide as thorax. Face approximately straight in profile, except for slight bulge below antenna; narrower than eye. Lateral oral margins strongly produced. Vertex flat. Occiput ventrally narrow, dorsally slightly widened. Antennal fossa about as wide as high. Eye bare. Eye margins in male parallel, not converging at level of frons, mutual distance about three times width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere shorter than scape; oval; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum deeply sulcate; almost entirely pilose, except bare on small part ventrally. Anepimeron entirely pilose. Katepimeron convex; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded; crossvein r-m located around basal 1/6 of cell dm. Abdomen elongate, more than 3 times as long as wide; in male gradually tapering from anterior half of tergite 2 to apex; in female slightly constricted between tergites 3 and 4. Tergites 3 and 4 fused. Male genitalia: phallus furcate basally, with dorsal process much longer than ventral one, projecting far beyond apex of hypandrium; epandrium with ventrolateral ridge; surstylus weakly furcate, divided into two short lobes.

Diagnosis. Vein R4+5 with posterior appendix. Postpronotum pilose. Anepisternum almost entirely pilose, except bare on small ventral part. Basoflagellomere shorter than scape. Abdomen at least three times as long as wide. Tergite 2 with pair of depressed areas (Fig. 287).

Discussion.

When Shiraki (1930) described Parocyptamus, this genus was diagnosed in a key by the following two characters: abdomen narrow and elongate, frons with antennal prominence (‘Fühlervorsprung’). The latter character is of limited use, as the frons is more or less extended above the antennae in many other taxa of Microdontinae. Hull (1937a) did not state which characters he considered diagnostic in his description of Stenomicrodon. Judging from his remarks in Hull (1949), the shape of the abdomen and the presence of a patch of short, spinose setae at the base of the front and mid femora were considered important characters. Although the anterobasal patches of setae are well-developed, such patches are also found in several other taxa of Microdontinae. Perhaps the spines are somewhat stronger developed than in most taxa, but it is hard to describe this as a discrete character state. Therefore, this character is not used in the present key and Diagnosis.

The abdomen is constricted (slightly) only in the female, not in the male, as might be erroneously concluded from the key of Cheng and Thompson (2008).

The synonymy of Stenomicrodon with Parocyptamus was already established by Hull (1949). Examination of the involved type specimens by the first author has confirmed this (subjective) synonymy. The type species of both genus group names are here also considered as synonyms (Parocyptamus sonamii Shiraki, 1930 = Stenomicrodon purpureus Hull, 1937 syn. n.). Microdon stenogaster Curran, 1931 also belongs to this genus, as it is almost identical to the type species in colouration, external morphology and male genitalia. Closer examination of available specimens, also from Sumatra and Thailand, is necessary to resolve species level taxonomy.

Shiraki (1930) based his description of Parocyptamus sonamii on three males. Two of these syntypes are kept in the NIAS collection. The third male (from Sokotsu) is apparently lost. Label information is as follows. Syntype 1: label 1: “Formosa, Shinchiku, -18. VII 1-30. J. Sonan, K. Miyake”; label 2: “Parocyptamus sonamii”; label 3 (round, red-bordered): “Type”. Syntype 2: label 1: “CIHpOn, 17.VII.1922, M. Yoshino”; label 2 (round, red-bordered): “Type”. The date on the label of syntype 1 is a bit cryptic (“-18. VII 1-30”). It is unlikely to assume the specimen has been collected in July 1930, because Shiraki’s work was published on the 30th of January 1930. It seems more plausible that the date was 1-30 July 1918. Shiraki (1930) only mentions the month (VII).

Diversity and distribution.

Described species: 2. Oriental: known from Taiwan, Thailand, Sumatra and Borneo.

Type species:

Mulio bidens Fabricius, 1805. Type locality: “America Meridionalo”.

Description.

Body length: 6–18 mm. Slender to moderately broadly built flies with oval or basally constricted abdomen and long antennae. Head wider than thorax. Face straight to slightly convex or slightly concave in dorsal half; narrower to wider than an eye; medially with vitta of transversely wrinkled texture (except in some smaller species of the flavofascium-group); gena distinctly ventrally produced. Lateral oral margins produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male converging at level of frons, with mutual distance 1.5-4 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape; bare. Postpronotum pilose or bare. Scutellum semicircular; with calcars. Anepisternum sulcate; pilose anterodorsally and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron flat; with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 more or less straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded, without appendix; crossvein r-m located between basal 1/6 and 1/3 of cell dm. Abdomen oval or basally constricted, 2-4 times as long as wide. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus not or little projecting beyond apex of hypandrium, slightly bent dorsad, shallowly furcate, with both processes about equally long and with their apexes wide at the furcation point but pointed apically; epandrium without ventrolateral ridge; surstylus unfurcate.

Diagnosis.

Vein R4+5 with posterior appendix. Postero-apical corner of cell r4+5 widely rounded. Katepimeron flat, with wrinkled texture, bare. Face in profile slightly convex, straight or slightly concave, but never bulged in ventral half. Vertex flat.

Three species groups are recognized here. These groups may not be monophyletic, but they may be useful for purposes of species identification. They are diagnosed as follows:

bidens-group: Abdomen oval or parallel-sided. Tergites without golden pile. Basoflagellomere less than twice as long as scape.

flavofascium-group: Abdomen oval. Tergite 4 often with golden or silver pile. If not, then basoflagellomere more than twice as long as scape.

trivittatus-group: Abdomen constricted basally.

Discussion.

The species here assigned to this genus (see Appendix 2) used to be placed in Microdon (e.g. Thompson et al. 1976), but the results of the phylogenetic analyses by Reemer and Ståhls (in press) indicate that they do not belong there. Based on external characters this group is difficult to diagnose, but usually the species can be distinguished at a glance from those of Microdon because of their more or less elongate (sometimes constricted) abdomen. In addition, morphology of the phallus is very constant (differences with Microdon in parentheses): projecting not or little beyond apex of hypandrium (far beyond apex of hypandrium), slightly bent dorsad (strongly bent), shallowly furcate (deeply furcate), with both processes about equally long and with their apexes wide at the furcation point but pointed apically.

Only one species here included in Peradon was previously not classified in Microdon: Ubristes chrysopygus Giglio-Tos, 1892.

Diversity and distribution.

Described species: 24. Neotropical. Several undescribed species are known to the first author.

Etymology.

The generic name is a combination of the Greek words peras (west) and odon, with the latter used as a suffix derived from Microdon. The prefix pera- is used to emphasize that this genus is restricted in its distribution to the western hemisphere.

Type species:

Piruwa phaecada spec. n. Type locality: Peru, Sachavacayoc.

Description.

Body length: 4 mm. Small, slender flies with short antennae and constricted abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput narrow over entire length. Eye bare. Eye margins in male not converging at level of frons, with mutual distance 3 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval, about twice as long as wide, bare. Postpronotum bare. Scutellum semicircular; without calcars; with long bristly pile along margin, clearly longer and thicker than pile on rest of scutellum. Anepisternum convex; pilose anterodorsally and along posterodorsal margin. Anepimeron pilose along dorsal margin. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located within basal 1/10 of cell dm. Abdomen constricted, narrowest at transition between tergites 1 and 2, widest at tergite 4; about 2.5 times as long as wide. Tergites 3 and 4 fused, no suture visible. Sternite 1 bare. Male genitalia: phallus furcate near apex, slightly bent dorsad, projecting only a little beyond apex of hypandrium; hypandrium with bulb-like base, with apical part entire, not consisting of two separate lobes; epandrium without ventrolateral ridge; surstylus consisting of two lobes, with basal lobe angular, apical lobe rounded.

Diagnosis.

Vein R4+5 without posterior appendix. Antenna shorter than distance between antennal fossa and anterior oral margin. Postpronotum bare. Abdomen constricted.

Discussion.

Although there is a superficial similarity in habitus to Paramicrodon (small, slender, short antennae, vein R4+5 without posterior appendix), Piruwa differs from that genus in the following important characters: occiput narrow over entire length; postpronotum bare; scutellum with long bristly pile along margin; anepimeron pilose only along dorsal margin; sternites 3-4 about as wide as sternite 2; hypandrium with apical part not consisting of two separate lobes. Considering these differences, a close relationship between these taxa seems unlikely. Because of these differences and the uncertainy of taxonomic affinities, this distinct taxon is given generic rank.

Diversity and distribution.

Described species: 1. Neotropical. Only known from Peru.

Etymology.

The name Piruwa is derived from Piruw, the word for Peru in Quechuan, a native Andean-Ecuadorian language. It is to be treated as feminine.

Pseudomicrodon Hull

http://species-id.net/wiki/Pseudomicrodon

Figs 307–320
Pseudomicrodon Hull, 1937a: 24. Type species: Microdon beebei Curran, 1936: 4, by original designation.
Description.

Body length: 7–9 mm. Slender flies with long antennae and petiolate abdomen. Head a little wider than thorax. Face more convex or straight in profile; narrower than to as wide as an eye. Lateral oral margins weakly produced. Vertex convex and shining; sparsely pilose, sometimes bare on anterior half. Occiput ventrally narrow, dorsally strongly widened. Eye bare or with very short and sparse pile. Eye margins in male converging at level of frons, with mutual distance 1-2 times width of antennal fossa. Antennal fossa about as wide as high to 1.5 times as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; with or without calcars. Anepisternum sulcate; entirely pilose or widely bare medially. Anepimeron entirely pilose. Katepimeron flat to convex; usually with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded to rectangular, with or without small appendix; crossvein r-m located between basal 1/6 to 1/3 of cell dm. Abdomen elongate, more than three times as long as wide, constricted, with narrowest point between halfway tergite 2 and transition between tergites 2 and 3. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus furcate near apex, with dorsal process long and whip-like, ventral process very short; epandrium with ventrolateral ridge.

Diagnosis.

Vein R4+5 with posterior appendix. Vertex convex and shining, sparsely pilose to bare. Abdomen petiolate, except parallel-sided in Pseudomicrodon biluminiferus Hull, but tergite 2 distinctly dorsoventrally flattened in that species.

Discussion.

Among Microdontinae with a petiolate abdomen, Pseudomicrodon species are recognized by their convex and shining vertex. Microdon biluminiferus Hull, 1944 is the only included species without a petiolate abdomen. Instead, the abdomen is parallel-sided, but in lateral view appears constricted because of the dorsoventrally flattened segment 2. This species is assigned to Pseudomicrodon based on the convex vertex and the morphology of the male genitalia (Figs 319, 320), combined with the results of the phylogenetic analysis of morphological characters (Reemer and Ståhls in press).

At present, the basis for distinguishing Ceriomicrodon, Pseudomicrodon and Rhopalosyrphus is narrow. The groups are certainly related, but as presently defined it is doubtful whether they are monophyletic, considering the variation in several morphological characters.

Keiser (1971) described Pseudomicrodon elisabethae from Madagascar. This species is here included in Paramixogaster. Cheng and Thompson (2008) mention the similarity of the South African taxon Microdon illucens Bezzi, 1915 to Pseudomicrodon, which is here also included in Paramixogaster.

Diversity and distribution.

Described species: 15. Neotropical.

Ptilobactrum Bezzi

http://species-id.net/wiki/Ptilobactrum

Figs 321–326
Ptilobactrum Bezzi, 1915: 136. Type species: Ptilobactrum neavei Bezzi, 1915: 137, by original designation.
Description.

Body length: 13 mm. Broadly built flies with very wide head, long antennae and orange markings on abdomen. Head wider than thorax. Face much wider than eye; dorsally with oblique groove from lunule to eye margin; convex in profile. Lateral oral margins weakly produced. Vertex not swollen, more or less flat, but much wider than eye. Occiput narrow ventrally, moderately widened dorsally. Eye bare. Eye margins in male not converging at level of frons, with mutual distance about seven times width of antennal fossa. Antennal fossa somewhat higher than wide. Antenna longer than height of head. Basoflagellomere five times as long as scape; with long pilosity. Postpronotum pilose. Mesoscutum with transverse suture incomplete. Scutellum without calcars. Anepisternum with deep sulcus; entirely pilose. Anepimeron entirely pilose. Katepimeron convex; smooth; bare. Wing: vein R4+5 with posterior appendix; vein M1 straight, somewhat recurrent; postero-apical corner of cell r4+5 angular, with small appendix; crossvein r-m located around basal 1/3 of cell dm. Abdomen oval, widest at posterior margin of tergite 2. Tergites 3 and 4 fused. Sternite 1 bare. Sternite 4 in male visible from below. Male genitalia: phallus bent dorsad, except extreme apex bent ventrad; phallus furcate near apex; epandrium without ventrolateral ridge; surstylus broad, unfurcate, with short posterior lobe. Female unknown.

Diagnosis.

Vein R4+5 with posterior appendix. Basoflagellomere with long pile. Abdomen oval. Tergites 3 and 4 fused.

Discussion.

Bezzi (1915) distinguished Ptilobactrum from Microdon species by the “breadth of the head, the face being furrowed, and by the unusual shape of the antennae.” Indeed, the grooves on the face, running fom the lunula obliquely downward to the eye margins, are quite unusual among Microdontinae. They are reminescent of the ptilinal sutures of Diptera Schizophora. Similar grooves are found in certain species of Furcantenna, Schizoceratomyia, Paramixogaster and Thompsodon, but usually less distinct. The antennae are unusual in their long pilosity, a character shared with Ceratrichomyia, Furcantenna, Kryptopyga and Schizoceratomyia.

See Ceratrichomyia for a discussion on synonymy of that genus with Ptilobactrum, as proposed by Cheng and Thompson (2008).

Diversity and distribution.

Described species: 1. Afrotropical, only known from Kenya.

Rhoga Walker

http://species-id.net/wiki/Rhoga

Figs 327–331
Rhoga Walker, 1857: 157. Type species: Rhoga lutescens Walker, 1857: 157, by monotypy.
Papiliomyia Hull, 1937a: 27. Type species: Papiliomyia sepulchrasilva Hull, 1937: 28, by original designation. For synonymy see Hull (1949).
Description.

Body length: 5–10 mm. Stingless bee mimicking flies with short to moderately long antennae and oval, kite-shaped or more or less parallel-sided abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex narrow, convexly produced and shining in most species, flat in some. Occiput wide and parallel-sided over entire length. Eye with short, sparse pile. Eye margins in male not converging at level of frons, with mutual distance 2 to 3 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna as long as or shorter than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular, in some species weakly sulcate apicomedially; without calcars. Anepisternum without sulcus; pilose anterodorsally and posteriorly, widely bare in between. Anepimeron entirely pilose. Katepimeron convex; bare. Metapleurae either separated or forming postmetacoxal bridge. Wing: vein R4+5 without posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located within 1/4 of cell dm, usually within basal 1/10. Abdomen oval or kite-shaped, 1.5 to 2.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus furcate near apex, with dorsal and ventral process equally long; epandrium without ventrolateral ridge.

Diagnosis.

Vein R4+5 without posterior appendix. Occiput widened and parallel-sided over entire length.

Discussion.

In some species (e.g. Rhoga mellea (Curran, 1940), Rhoga maculata (Shannon, 1927)) the metapleura are separated and do not form a postmetacoxal bridge. So far in Microdontinae, this character state was known only in the genus Spheginobaccha (Cheng and Thompson 2008).

The type specimen of the type species, Rhoga lutescens Walker, 1857, is not present in the BMNH-collection (pers. comm. N. Wyatt), where it is supposed to be according to Thompson et al. (1976) and Thompson (2010). Apparently it is lost.

Diversity and distribution.

Described species: 5. Central and South America. Several undescribed species are known to the first author.

Rhopalosyrphus Giglio-Tos

http://species-id.net/wiki/Rhopalosyrphus

Figs 332–355
Rhopalosyrphus Giglio-Tos, 1891: 189. Type species: Holmbergia guentherii Lynch Arribalzaga, 1891, by subsequent designation of Giglio-Tos (1892: 2).
Holmbergia Lynch Arribalzaga, 1891: 196. Type species: Holmbergia guentherii, 1891: 195, by monotypy. See Weems et al. (2003) and Cheng and Thompson (2008) for synonymy.
Description.

Body length: 9–15 mm. Slender flies with long antennae and petiolate abdomen. Head a little wider than thorax. Face more or less convexly produced on ventral half; narrower than an eye. Lateral oral margins produced. Vertex flat, entirely pilose. Occiput ventrally narrow, dorsally strongly widened. Eye bare. Eye margins in male converging at level of frons, with mutual distance 1-2 times width of antennal fossa. Antennal fossa about 1.5 times as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular; with or without calcars, if present, then small and with mutual distance small. Anepisternum convex or with weak sulcus; entirely pilose. Anepimeron entirely pilose. Katepimeron flat to weakly convex; with wrinkled texture; bare, partly pilose or entirely pilose. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded to rectangular, with or without small appendix; crossvein r-m located between basal 1/8 to 1/4 of cell dm. Abdomen elongate, more than three times as long as wide, constricted, with narrowest point between halfway tergite 2 and transition between tergites 2 and 3. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus furcate near apex, with dorsal process long and whip-like, ventral process very short; epandrium with ventrolateral ridge.

Diagnosis.

Vein R4+5 with posterior appendix. Abdomen petiolate. Vertex flat, entirely pilose. Postpronotum pilose. Mesonotal transverse suture incomplete. Tergites 3 and 4 fused. Anterior margin of tergite 2 at least twice as wide as posterior margin. Rhopalosyrphus s.s.: katepimeron pilose. Rhopalosyrphus s.l.: katepimeron bare.

Discussion.

Previous authors have defined this genus more strictly than is done in the present paper. Weems et al. (2003) and Cheng and Thompson (2008) only included species with a pilose katepimeron. A number of additional species are known from the Neotropical region which are similar to Rhopalosyrphus auct. in most characters, but which have a bare or almost bare katepimeron. In Rhopalosyrphus robustus sp. n. the katepimeron is only narrowly pilose along the anterior margin. In all other characters, this species has the diagnostic characters of Rhopalosyrphus as described by Weems et al. (2003): abdomen petiolate, antenna longer than face, scape and basoflagellomere elongate, face produced ventrally (variable), occiput strongly widened dorsally, metasternum developed, hind tibia flared apically. The male genitalia of Rhopalosyrphus robustus are very similar to those of Rhopalosyrphus auct., with an apically furcate phallus, of which the dorsal process is very long and whip-like (Figs 352-355).

Microdon abnormis Curran, 1925 is also similar to Rhopalosyrphus in the characters mentioned above, but has a bare katepimeron. In the analysis of morphological characters by Reemer and Ståhls (in press), a closely related species (Rhopalosyrphus abnormoides sp. n.) is placed within Rhopalosyrphus.

Based on the results of the phylogenetic analyses and the (subjective) evaluation of external and genitalic characters, Rhopalosyrphus is here extended to include also the species with a bare or almost bare katepimeron, which includes species previously grouped in the abnormis group (see account of Pseudomicrodon in Cheng and Thompson 2008), as well as Microdon cerioides Hull, 1943. Species with a pilose katepimeron are included in Rhopalosyrphus s.s., while the other species are treated as Rhopalosyrphus s.l.

The inclusion of Rhopalosyrphus oreokawensis sp. n. in this genus is to be regarded as preliminary. Unlike the other species included in Rhopalosyrphus, this species has very short antennae, an oblique vein M1 and a more slender tergite 2. Analysis of its morphological characters (Reemer and Ståhls in press) resolves its phylogenetic position near Rhopalosyrphus. Possibly, it would be better to erect a new genus for this species. This is nevertheless not done here, in awaitance of a better understanding of the relationships of the taxa included in the ‘Rhopalosyrphus-clade’.

Diversity and distribution.

Described species: 9. Mainly Neotropical, with two species in southern parts of the U.S.A. (Arizona, Texas, Florida).

Schizoceratomyia Carrera, Lopes & Lane

http://species-id.net/wiki/Schizoceratomyia

Figs 356–363
Schizoceratomyia Carrera, Lopes & Lane, 1947a: 245. Type species: Schizoceratomyia barretoi Carrera, Lopes & Lane 1947a: 245, by original designation.
Johnsoniodon Curran, 1947: 1. Type species: Johnsoniodon malleri Curran, 1947: 1, by original designation. See Papavero (1962) for synonymy.
Description.

Body length: 4–9 mm. Broadly built flies with long antennae (bifrucate in male) and oval abdomen. Head wider than thorax. Face slightly convex or medially concave; wider than an eye. Mouth parts weakly developed, small; oral opening small and round, with lateral margins not produced. Vertex more or less flat, not strongly produced or convex. Frontal ocellus normal, split in two medially or absent. Occiput ventrally narrow, dorsally weakly widened. Eye bare. Eyes in male not or only slightly converging at level of frons, with mutual distance 3–4 times the width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin. Basoflagellomere longer than scape, bifurcate in male, in some species also in female; both branches long pilose, especially on inner side; in one (undescribed) species occupied with more than 20 long, narrow tubercles. Arista in male well-developed (longer than pedicel) or reduced to a small stump (shorter than pedicel); in female well-developed, sometimes almost as long as basoflagellomere and thickened. Postpronotum pilose or bare. Scutellum semicircular; without calcars. Anepisternum convex, sometimes with weak sulcus in dorsal 1/4; pilose on dorsal 2/3 to 3/4. Anepimeron pilose on dorsal 3/4 to 1/4, or only along posterior margin. Katepimeron convex; bare; smooth. Wing: vein R4+5 without posterior appendix; vein M1 straight and perpendicular to vein R4+5, or with weak outward angle in anterior 1/2; postero-apical corner of cell r4+5 rectangular to widely rounded, with or without small appendix; crossvein r-m located between basal 1/8 and 1/4 of cell dm. Abdomen dorsoventrally flattened; more oval, with largest width at tergite 3; 1.5-2 times as long as wide. Tergites 3 and 4 fused. Male genitalia: phallus furcate near apex, straight or apically bent ventrad, projecting not or hardly beyond apex of hypandrium; hypandrium with bulb-like base; epandrium without ventrolateral ridge; surstylus unfurcate, elongate or wide.

Diagnosis.

Vein R4+5 without posterior appendix. Abdomen oval. Antenna longer than distance between antennal fossa and anterior oral margin. Antenna inserted below dorsal eye margin. Vertex more or less flat. Katepisternum bare. Metasternum bare.

Discussion.

Hull (1949) and Papavero (1962) treated Schizoceratomyia as a synonym of Masarygus. See Masarygus for discussion on this synonymy, which is not followed here. These authors, as well as Cheng and Thompson (2008) also considered Johnsoniodon as a synonym of Schizoceratomyia, as is also done in the present paper. Although in the two species originally included in Schizoceratomyia (Schizoceratomyia barretoi Carrera, Lopes & Lane, 1947 and Schizoceratomyia flavipes Carrera, Lopes & Lane, 1947) the basoflagellomere is bifurcate in the male only, whereas in Johnsoniodon this character is found in the female, these taxa are otherwise very similar.

Apparently, Curran (1947) was unaware of the description of Schizoceratomyia by Carrera et al. (1947a, b) when his description of Johnsoniodon malleri Curran, 1947 was published, as this happened almost simultaneously. According to Van Doesburg (1966), the name Schizoceratomyia was published on the 3rd of July 1947, and Johnsoniodon on 14th of July 1947. Cheng and Thompson (2008) stated that Schizoceratomyia was published on the 12th of July 1947. Regardless of whether the date is 3rd or 12th of July Schizoceratomyia has priority over Johnsoniodon.

Besides Schizoceratomyia malleri (Curran), a furcate basoflagellomere in the female is also found in Masarygus carrerai Papavero, 1962. This species is also included in Schizoceratomyia.

Remarkably, in some specimens of Schizoceratomyia, the frontal ocellus is split in two, strongly reduced or even absent, whereas the posterior ocelli are well-developed. Following present species definitions, different states for this character seem to occur within the same species. However, more taxonomic work at species-level is necessary to establish whether this character state variation is intra- or inter-specific. In most Diptera and other flying insects, all three ocelli are well-developed. Reduced or absent ocelli occur in certain terrestrial insects, like certain ants and cockroaches. Among Diptera, they are partly or entirely absent only in a few groups, apparently mainly in certain nematocerous families and some brachypterous or apterous taxa (Cumming and Wood 2009). It will be interesting to try to correlate the degree of development of the frontal ocellus to behaviour and life-history of Schizoceratomyia-species; aspects which are currently unknown, unfortunately.

Diversity and distribution.

Described species: 4. Neoptropical. A few undescribed species are known to the first author.

Serichlamys Curran, stat. n.

http://species-id.net/wiki/Serichlamys

Figs 364–376
Serichlamys Curran, 1925a: 50. Type species: Aphritis rufipes Macquart, 1842: 71, by monotypy.
Description.

Body length: 7–13 mm. Small to medium-sized flies, black, brownish or metallic green, with moderately short to long antennae and oval abdomen. Head about as wide as thorax or slightly wider. Face convex; about as wide as an eye or narrower. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare or pilose. Eye margins in male converging at level of frons, with mutual distance two to four times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter to longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval or slightly sickle-shaped with swollen base, with rounded apex; bare. Postpronotum pilose. Scutellum semicircular; with narrow, elongated calcars, often quite parallel and with small mutual distance, sometimes dorsoventrally flattened. Anepisternum weakly sulcate; pilose anteriorly and posteriorly, widely bare ventrally and medially. Anepimeron entirely pilose. Katepimeron convex; smooth or with wrinkled texture; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular or weakly rounded, always with small appendix; crossvein r-m located between basal 1/5 to 1/3 of cell dm. Abdomen oval, about 1.5 to 2 times as long as wide. Tergites 3 and 4 fused. Sternite 1 pilose or bare. Male genitalia: phallus furcate, with furcation point near apex; hypandrium with basal part bulb-like; epandrium without ventrolateral ridge.

Diagnosis.

Vein R4+5 with posterior appendix. Abdomen oval. Vertex flat. Occiput dorsally (slightly) widened. Postpronotum pilose. Scutellum with calcars. Postero-apical corner of cell r4+5 rectangular, with small appendix. Proepimeron pilose. Anepisternum widely bare medially, also on dorsal half. Anepimeron entirely pilose. Male genitalia: phallus furcate near apex.

Discussion.

Curran (1925a) erected Serichlamys as a subgenus of Microdon, but subsequent authors considered Serichlamys as a synonym of the typic subgenus of Microdon (Wirth et al. 1965, Thompson 1981b, Cheng and Thompson 2008). Curran (1925a) did not clearly state which characters he considered diagnostic. In his key, Curran keyed out the type species Microdon rufipes (Macquart, 1842) by its eyes being pilose, which was based on a translation of the original description of Aphritis rufipes. Indeed, Macquart (1842) wrote that this species has ‘yeux peu velus’ (eyes little pilose). However, examination of the type specimen (coll. OUMNH) revealed that its eyes are bare. Either pile have been wiped off or eroded in the course of time, or Macquart (1842) made an error in his description. Whether Aphritis rufipes has pilose eyes or not, Serichlamys is here recognized as distinct as all included species differ in other characters from Microdon s.s., e.g. postero-apical corner of cell r4+5 rectangular (rounded in Microdon s.s.), phallus furcate apically, hypandrium with bulb-like base.

The differences with Microdon s.s. could be used as arguments for reinstating the subgeneric status of Serichlamys. However, a subgeneric status is contradicted by the phylogenetic results of Reemer and Ståhls (in press), who recovered two Neotropical species of Serichlamys as sister group to Archimicrodon, without apparent close affinities to Microdon. The type species Serichlamys rufipes and Serichlamys scutifer (Knab, 1917) were included in a phylogenetic analysis based only on morphology, and placed in a large and rather uninformative polytomy, but not within a clade containing species of Microdon s.s. For this reason, Serichlamys is here raised to genus level.

Three Nearctic species are included in Serichlamys: Serichlamys rufipes (Macquart, 1842), Serichlamys scutifer (Knab, 1917), and Serichlamys diversipilosus (Curran, 1925). The latter species is included with uncertainty, based only on the description, as no specimens were examined. Two Neotropical species are included: Serichlamys mitis (Curran, 1940) and Serichlamys mus (Curran, 1936). The Neotropical species differ from the Nearctic ones in the shape of the surstylus, which has a long posterior process which is lacking in the Nearctic species. Otherwise the species are very similar. Species of Serichlamys quite similar to the Old World genus Archimicrodon in general habitus and important morphological characters, including the male genitalia. Generally, the antennae of Serichlamys-species are longer and the scutellar calcars are longer.

Diversity and distribution.

Described species: 4 or 5. Nearctic (2 or 3 described species) and Neotropical (2 described species). Several undescribed species from the Neotropical regioan are known to the first author.

Spheginobaccha de Meijere

http://species-id.net/wiki/Spheginobaccha

Figs 377–387
Spheginobaccha de Meijere, 1908: 327. Type species: macropoda Bigot, 1883: 331, by monotypy.
Dexiosyrphus Hull, 1944a: 131. Type species: Spheginobaccha funeralis Hull, 1944: 131, by original designation. Described as subgenus of Spheginobaccha.
Description.

Body length: 7–19 mm. Slender flies with short antennae and constricted abdomen. Head about as wide as to wider than thorax. Face in profile straight to slightly concave in dorsal 2/3, with a faint convex tubercle in ventral 1/3; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput narrow ventrally, widening dorsally, with distinct crease in dorsal 2/3. Eye bare (African species) or short pilose (Oriental species). Eyes in male not (African species) or strongly (Oriental species) converging at level of frons, in one Oriental species (Spheginobaccha chilcotti Thompson) even nearly contiguous. Antennal fossa about twice as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin. Basoflagellomere longer than scape, oval, except more or less triangularly enlarged in males of some African species; bare. Postpronotum pilose. Scutellum semicircular; without calcars. Anepisternum without sulcus; entirely sparsely pilose, sparsely pilose only posteriorly, or entirely bare. Anepimeron pilose on dorsal half or bare. Katepimeron flat; bare or pilose; smooth. Wing vein R4+5 without posterior appendix. Vein M1 oblique and more or less parallel to wing margin, in African species only so in anterior 1/2, posterior 1/2 straight. Postero-apical corner of cell widely rounded and without appendix in Oriental species, rectangular and with appendix in African species. Crossvein r-m located between basal 1/6 to 1/3 of cell dm. Abdomen constricted, narrowest halfway or at posterior margin of tergite 2, widest at tergite 4. Tergites 3 and 4 fused. Male genitalia: phallus unfurcate, straight (African species) or bent dorsad (Oriental species), articulating with hypandrium apically (perialla-group) or basally (macropoda- and rotundiceps-group); hypandrium with apical part consisting of separate lobes; epandrium without ventrolateral ridge; surstylus unfurcate, oval or more or less rectangular to triangular.

Diagnosis.

Metapleura not connected, not forming a postmetacoxal bridge. Abdomen constricted. Occiput with deep crease on dorsal 2/3.

Discussion.

Hull (1949) was the first to include Spheginobaccha in the Microdontinae. Thompson (1969) excluded it, after which Ståhls et al. (2003) included it again. The latter placement was based on a sister-group relationship of Spheginobaccha to all other Microdontinae, as recovered in a phylogenetic analysis of combined molecular and morphological characters. Species can be identified using Thompson (1974), supplemented with Dirickx (1995).

Dexiosyrphus was described by Hull (1949) as a subgenus of Spheginobaccha, based on Spheginobaccha rotundiceps (Loew, 1857). Thompson (1974) argued that if Dexiosyrphus was to be recognized, then another subgenus would have to be erected for the perialla-group. He considered this unnecessary, as the three species groups he recognized were sufficient for proper segregation of the species. We see no reason to adopt a different point of view.

Diversity and distribution.

Described species: 16. Oriental (10 species) and Afrotropical (6 species). Oriental records range from Nepal through Burma, Thailand and Vietnam to Java and Borneo. Afrotropical records are from Malawi, South Africa and Madagascar.

Stipomorpha Hull, stat. n.

http://species-id.net/wiki/Stipomorpha

Figs 388–396
Stipomorpha Hull, 1945: 74. Type species: Microdon fraudator Shannon, 1927, by original designation.
Description.

Body length: 6–11 mm. Stingless bee mimicking flies with moderately long antennae and more or less triangular abdomen. Head slightly wider than thorax. Face in profile straight to convex; narrower to wider than an eye. Lateral oral margins hardly to moderately produced. Vertex flat, convex or irregularly swollen. Occiput narrow ventrally, slightly widened dorsally. Eye bare. Eye margins in male converging at level of frons, with mutual distance 1–3 times width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter to longer than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval; bare. Postpronotum pilose. Scutellum semicircular, sometimes weakly sulcate apicomedially; without calcars. Anepisternum convex, without sulcus; anterodorsally pilose, posteriorly pilose or bare, widely bare in between. Anepimeron with pile limited to dorsal half, if pilose on ventral half then only sparsely. Katepimeron convex; bare. Wing: vein R4+5 usually with posterior appendix (seldomly missing); vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 widely rounded to rectangular, with or without small appendix; crossvein r-m located between basal 1/5 to 1/3 of cell dm. Abdomen widest at tergite 2, with next tergites either gradually narrowing (kite-shaped abdomen) or more or less parallel-sided; 1.5 to 3.5 times as long as wide. Antetergite almost fused to tergite 1; in most species enlarged, concave and smooth. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus unfurcate, bent dorsad, in most species projecting beyond apex of hypandrium; hypandrium with bulb-like base; epandrium without ventrolateral ridge; surstylus in most species with two wide lobes, but other shapes also occur.

Diagnosis.

Sternites 2 and 3 separated by membraneous part as wide as or wider than sternite 2.

Discussion.

When Hull (1945) erected Stipomorpha as a subgenus of Microdon, he did so based on the shape of the abdomen: “...the first two abdominal segments greatly flared and flattened and wider than the thorax; remainder of the abdomen immediately compressed into a rounded, subcylindrical pipe-like form.” Shortly after, Hull (1949) ranked Stipomorpha as a subgenus of Paramixogasteroides Shiraki, 1930, without stating a reason for this. Subsequent authors have regarded Stipomorpha as synonymous with Ubristes. See under Ubristes for a discussion on the relationship between these groups, which are here considered as separate genera. Stipomorpha as presently defined contains most species listed under Ubristes by Thompson et al. (1976).

Diversity and distribution.

Described species: 16. Descriptions of nine additional species are in preparation by the first author. Neotropical, with records ranging from Costa Rica to Argentina.

Type species:

Microdon sulcatus Hull, 1944: 256. Type locality: Java, Soekaboemi.

Description.

Body length: 7–9 mm. Broadly built flies with moderately long antennae and short abdomen. Head about as wide as thorax or slightly wider. Face convex; about as wide as an eye. Lateral oral margins distinctly produced. Vertex irregularly swollen. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male converging at level of frons, with mutual distance 2.5 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere about as long as to slightly longer than scape, parallel-sided; bare. Postpronotum bare. Scutellum semicircular; with large, blunt calcars, separated by deep sulcus. Anepisternum weakly sulcate; entirely pilose. Anepimeron entirely pilose. Katepimeron flat; bare. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located around basal 1/4 of cell dm. Abdomen heart-shaped, about as long as wide. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus furcate, with furcation point near apex; hypandrium with basal part bulb-like; epandrium without ventrolateral ridge; surstylus deeply furcate.

Diagnosis.

Postpronotum bare. Abdomen about as long as wide, with tergite 2 about as long as tergites 3 and 4 together.

Discussion.

The only species included in this group, the Oriental Microdon sulcatus Hull, 1944, does not have any obvious relatives. Because of the bare postpronotum, the rectangular postero-apical corner of cell r4+5, the entirely pilose anepisternum and the characters of the male genitalia, the species does not fit into Microdon s.s.

Diversity and distribution.

Described species: 1. Indonesia: Java. The species seems not to be uncommon, as specimens collected by different collectors in different years are present in several entomological collections (BMNH, KBIN, MZH, RMNH, ZMAN). Although entomological collectors have been active in other parts of the Sunda region, such as peninsular Malaysia, Sumatra and Borneo, this species has so far not been found there. This suggests that this singular species is endemic to Java.

Etymology.

The generic name is composed of sulcus and odon. The first part means ‘furrow’ or ‘groove’ in Latin, but in this case it is derived from Microdon sulcatus, the type species of the genus. The second part of the name is used as a suffix derived from Microdon.

Surimyia Reemer

http://species-id.net/wiki/Surimyia

Figs 400–405
Surimyia Reemer, 2008: 179. Type species: Surimyia rolanderi Reemer, 2008: 180, by original designation.
Description.

Body length: 4–5 mm. Small flies with short antennae and oval abdomen. Head slightly wider than thorax. Face convex; narrower than an eye. Lateral oral margins not produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye bare. Eye margins in male not converging at level of frons, with mutual distance about 3 times as large as width of antennal fossa. Antennal fossa about as wide as high. Antenna shorter than distance between antennal fossa and anterior oral margin; basoflagellomere shorter to longer than scape, oval, about twice as long as wide, bare. Postpronotum bare. Scutellum semicircular; without calcars. Anepisternum convex; dorsally with thick, setae-like pile, ventrally bare. Anepimeron dorsally with thick, setae-like pile, ventrally bare. Katepimeron convex; bare. Wing: vein R4+5 without posterior appendix; vein M1 straight, perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with or without small appendix; crossvein r-m located very close to base of cell dm. Abdomen oval, about 1.5 times as long as wide. Tergites 3 and 4 fused. Sternite 1 bare. Male genitalia: phallus furcate, with furcation point about halfway, curved dorsad, straight, projecting not or slightly beyond apex of hypandrium; hypandrium without bulb-like base; epandrium without ventrolateral ridge; surstylus unfurcate.

Diagnosis.

Abdomen oval; yellow and black. Vein R4+5 without posterior appendix. Postpronotum bare. Antenna shorter than distance between antennal fossa and anterior oral margin.

Discussion.

Reemer (2008) included in his new genus Surimyia a species previously assigned to Paragodon (Paragodon minutula van Doesburg, 1966). Several morphological characters were mentioned to indicate the differences between these genera (Reemer 2008). Especially the structure of the phallus seems fundamentally different: short, straight and unfurcate in Paragodon, and long, curved and bifurcate in Surimyia. Other distinctive differences are the bare postpronotum in Surimyia (pilose in Paragodon) and the bare anatergum in Surimyia (microtrichose in Paragodon).

Diversity and distribution.

Described species: 2. Neotropical (presently only known from Surinam).

Syrphipogon Hull (subgenus, see Microdon)
Type species:

Thompsodon conspicillifrons Reemer spec. n. Type locality: Costa Rica.

Description.

Body length: 8 mm. Moderately slender flies with long antennae and basally constricted abdomen. Face in profile slightly convex, almost straight; laterally weakly depressed, therefore slightly carinate dorsomedially; about as wide as an eye. Lateral oral margins not produced. Frons laterally with round, concave areas, filled with dense golden pile, ventrally delimited by a sharply defined ridge. Vertex irregularly swollen. Occiput narrow ventrally, strongly widened dorsally. Eye bare. Antennal fossa about as high as wide. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere about as long as scape; elongate, with dorsal margin straight and ventral margin convex, apex slightly acute. Postpronotum pilose. Anepisternum with shallow sulcus; entirely long pilose. Anepimeron entirely pilose. Katepimeron weakly convex; bare; with wrinkled texture. Scutellum semicircular, weakly triangular; without calcars. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; postero-apical corner of cell r4+5 rectangular, with small appendix; crossvein r-m located around basal 1/7 of cell dm. Abdomen constricted at tergite 1, narrowest at tergite 1, widest at posterior margin of tergite 3. Tergites 3 and 4 not fused, able to articulate independently.

Diagnosis.

Frons laterally with round, concave areas, filled with dense golden pile, ventrally delimited by a sharply defined ridge. Transverse suture complete. Tergites 3 and 4 not fused.

Discussion.

The only known specimen representing this genus has some characters that are not often found among Microdontinae: mesonotal transverse suture complete, tergites 3 and 4 not fused. The lateral concave and densely golden pilose areas on the frons, which are ventrally delimited by a sharply defined ridge, are even unique within the subfamily. The unfused tergites 3 and 4 may suggest affinity with the Neotropical Ceratophya or the Oriental Kryptopyga, whereas the complete transverse suture reminds of Ceratrichomyia andIndascia. However, the specimen does not agree with the diagnoses of any of these genera, so a new genus seems the best way to make sure that this singular taxon will get the attention it deserves in future studies on the taxonomy of Microdontinae. Hopefully, male specimens will be collected in the near future, which can be used for study of the male genitalia and molecular analyses.

Diversity and distribution.

Described species: 1. Only known from Costa Rica.

Etymology.

This genus is dedicated to Dr. F. Christian Thompson, in acknowledgement of the valuable work he has done on the taxonomy of the Syrphidae in general, and the Microdontinae in particular.

Ubristes Walker

http://species-id.net/wiki/Ubristes

Figs 417–421
Ubristes Walker, 1852: 217. Type species: Ubristes flavitibia Walker, 1852: 217, by original designation.
Description.

Body length: 10–11 mm. Slender flies with long antennae and long, brush-like pilosity on hind tibiae. Mimics of Trigona-like stingless bees. Head wider than thorax. Face slightly convex, almost straight in lateral view; wider than eye. Lateral oral margins produced. Vertex flat. Occiput ventrally narrow, dorsally widened. Eye very sparsely and short pilose, appearing bare under low magnification. Eye margins in male converging at level of frons; mutual distance about three times width of antennal fossa. Antennal fossa about as high as wide. Antenna longer than distance between antennal fossa and anterior oral margin; basoflagellomere longer than scape. Postpronotum pilose. Anepisternum sulcate; pilose anteriorly and posteriorly, widely bare in between. Katepimeron convex; bare. Scutellum semicircular; without calcars. Wing: vein R4+5 with posterior appendix; vein M1 perpendicular to vein R4+5; cell r4+5 with postero-apical angle widely rounded; crossvein r-m located between basal 2/5 and 1/2 of cell dm. Hind tibia with long, brush-like pilosity. Abdomen elongate: parallel-sided or somewhat triangular. Tergite 2 with lateral tubercle at half of length. Tergites 3 and 4 fused. Sternites 1, 2 and 3 not separated by very wide membranes. Male genitalia: phallus furcate basally; epandrium with lateral ‘fenestrae’: well-defined, translucent, oval depressions; surstylus more or less oval.

Diagnosis.

Hind tibia with long, brush-like pilosity. Scutellum without calcars. Vein R4+5 with appendix. Tergite 2 with lateral tubercle at half of length.

Discussion.

Thusfar, Ubristes has been characterized by the brush-like pilosity of the hind tibia, giving the flies the appearance of stingless Trigona-like bees (Cheng and Thompson 2008, Thompson et al. 1976). Based on this definition, 31 species were assigned to this group by Thompson et al. (1976), including the type species of Carreramyia, Hypselosyrphus and Stipomorpha. The latter two groups were considered as ‘subgroups’ of Ubristes by Cheng and Thompson (2008), because the characters previously used to define the groups (abdominal shape) were considered of little taxonomic value.

Closer examination of the morphology reveals several important differences between these taxa. The structure of the male genitalia of Ubristes is very different from those of the species here included in Carreramyia, Hypselosyrphus and Stipomorpha: the phallus is long and slender and furcate near its base, the base of the hypandrium is not bulged and there are well-defined, translucent, oval lateral depressions in the epandrium (here called ‘fenestrae’). In external morphology Ubristes is readily distinguished from the mentioned genera by e.g. the lateral tubercles on tergite 2. For other differences see the accounts of the other taxa. Considering the phylogenetic results of Reemer and Ståhls (in press) and the morphological differences between these taxa, Ubristes sensu Thompson et al. (1976) and Cheng and Thompson (2008) is here considered to be polyphyletic, with Carreramyia, Hypselosyrphus and Stipomorpha each as separate lineages. Besides the type species, two undescribed species are assigned to Ubristes.

Thompson et al. (1976) and Cheng and Thompson (2008) ranked Ubristes as a subgenus of Microdon. However, the species of Ubristes differ in several characters from the species of Microdon s.s., as defined in the present paper. Here, the view is taken that it is better to treat Ubristes as a genus instead of a subgenus, in order to make sure that Microdon comprises less heterogeneous groups with uncertain affinities.

Diversity and distribution.

Described species: 1. Descriptions of two additional species are in preparation by the first author. Central and South America.

Undescribed genus #1 Figs 422–426
Based on species AUS-01 of F.C. Thompson, in prep.
Diagnosis.

Basoflagellomere strongly widened, more or less triangular. Arista pilose.

Discussion.

This species has first been recognized as undescribed by Dr. F.C. Thompson, who is preparing a description of it. As the species posesses some unique characters not found in any other species of Microdontinae, the present authors feel that it belongs in a new genus. These characters are: basoflagellomere strongly widened and more or less triangular; arista pilose; phallus dorsobasally with long projection; epandrium with dorsolateral ridge. Other interesting characters are the undeveloped mouthparts (shared with Masarygus) and the lateral carinae on the face.

Diversity and distribution.

Described species: 1. Australia (Queensland).

Undescribed genus #2 Figs 427 –432
Based on species MCR-2 of F.C. Thompson, in prep.
Diagnosis.

Basoflagellomere bifurcate. Abdomen more or less parallel-sided, slightly constricted between tergites 2 and 3.

Discussion.

This species has first been recognized as undescribed by Dr. F.C. Thompson, who is preparing a description of it. This taxon resembles Carreramyia in the bifurcate antenna, the wing venation and the structure of the male genitalia. It differs from that genus by the more or less flat vertex (strongly produced in Carreramyia), the short pilose hind tibia (long pilose in Carreramyia), and the more or less parallel-sided, slightly constricted abdomen (triangular in Carreramyia).

Diversity and distribution.

Only known from one species, collected in Costa Rica.


Unplaced taxa

A small number of species is left unclassified. These are listed at the end of the following section on species classification. On a few of these taxa, comments are given below.

Microdon sharpii Mik, 1900
Figs 433–434
Discussion.

Based on external characters, no close relatives were recovered in the phylogenetic analysis of morphological characters by Reemer and Ståhls (in press). The species is characterized by its metallic blue colouration and golden pilosity, a long basoflagellomere, a medially widely bare face, a rectangular postero-apical corner of wing cell r4+5, and unfused tergites 3 and 4. The latter character may indicate affinity with Ceratophya, Kryptopyga or Thompsodon, but the species lacks other diagnostic characters for these taxa. This species is left unplaced for now.

Nothomicrodon Wheeler, 1924
Discussion.

Whether this taxon belongs to Microdontinae or Syrphidae at all is uncertain. It was described from larvae found in an ants nest (Wheeler 1924). Cheng and Thompson (2008) suspect it belongs to another family, perhaps Phoridae. Photographs of a larva can be found at http://syrphidae.lifedesks.org/pages/25523.

Discussion: diagnostic characters of Microdontinae

In order to find diagnostic characters for distinguishing Microdontinae from other Syrphidae, characters described by Hippa and Ståhls (2005), Hull (1949), Shatalkin (1975a, b), Speight (1987) and Thompson (1969, 1972) were evaluated based on the material examined for this study. The discussion of these characters below is subdivided into paragraphs corresponding with the following main body parts: head, thorax, wings, legs, abdomen, male genitalia. Terminology of the aforementioned authors is translated into the terminology used in the present paper (see section Material and Methods). This discussion concludes with a summarizing statement on diagnostic morphological characters of Microdontinae.

Head

The simple, convex face of most Microdontinae has been used as a character for the group by Hull (1949) and Thompson (1969, 1972). A facial tubercle is only found in Eurypterosyrphus. In a few taxa (Ceratrichomyia, Chrysidimyia, Rhopalosyrphus) the ventral part of the face is somewhat bulged, but cannot be considered tuberculate. The diagnostic value of this character is limited, as the facial tubercle is also missing in several other Syrphidae, e.g. all Pipizini and Eumerini.

According to Thompson (1969, 1972), the face of Microdontinae is uniformly pilose. In the present study, however, several taxa were found in which the face is bare medially to varying extent (e.g. species of Rhoga, Schizoceratomyia, Stipomorpha), sometimes even entirely bare (e.g. Masarygus planifrons).

Thompson (1972) noted that the anterior oral margin in Microdontinae is not notched. There seems to be some confusion about the interpretation of this character, as Hippa and Ståhls (2005) have coded this character as ‘medially notched’ for Microdon analis (Macquart, 1842). Apparently, the latter authors have regarded the anterior oral margin as notched when the lateral oral margins are produced. Indeed, these laterally produced oral margins give the impression in anterior view that the anterior oral margin is narrowed (notched). In most other Syrphidae (except Pipizini), however, there is a slight additional narrowing at the extreme anterior part of the oral margin (see e.g. fig. 3 in Speight 1987 and fig. 1A in Hippa and Ståhls 2005). This additional narrowing seems to be correlated with the presence of an anteclypeus. In Microdontinae, no distinction can be made between an anteclypeus and a postclypeus (see below), so this additional narrowing of the anterior margin is not visible. In the present study, we follow Hippa and Ståhls (2005) in the interpretation of this character. Many Microdontinae were found with produced lateral oral margins, as it is in most other Syrphidae, so this character is not considered to be useful for distinguishing the subfamily from other Syrphidae.

According to Speight (1987), Microdontinae possess only one clypeus, whereas an anteclypeus and a postclypeus can be recognized in other Syrphidae. The presence of only one clypeus in Microdontinae can be confirmed based on the present study, but the character has not been studied in other Syrphidae. Speight (1987) mentioned two other characters of the mouthparts he considered to be unique for Microdon: 1. the maxillary sclerites are short, flange-like, oriented transversely rather than longitudinally; 2. the maxillary palps are rudimentary. These characters have not been studied in the present study, and thus cannot be commented upon. In general, the mouthparts of Microdontinae are reduced compared with other Syrphidae. No characters indicating the degree of reduction were included in the present study, but a considerable degree of variation was noticed. In certain taxa, the labella are well-developed and flattened, suggesting a capability of feeding on flat surfaces (e.g. leaves) (this can best be noticed in fresh or alcohol-preserved specimens, as the mouthparts tend to shrivel up when dry). In other taxa, the mouthparts are reduced to such an extent that there is not even an oral opening, indicating these species do not feed at all (Masarygus palmipalpus sp. n., Masarygus planifrons).

Unlike most other Syrphidae, the males are dichoptic (i.e. the eyes do not meet at the top of the head). In the present study, no holoptic Microdontinae were found except for Spheginobaccha chillcotti Thompson, 1974, although in a few taxa the male eyes approach each other quite closely (e.g. Hypselosyrphus). When taken into consideration that dichoptic males also occur in other subfamilies of Syrphidae (e.g. Helophilus Meigen, 1822 and related genera, Neoascia Williston, 1887, Pelecocera Meigen, 1822), this character has limited diagnostic value.

According to Thompson (1969, 1972) the arista of Microdontinae is bare. The only known exception, as found in the present study, is the Australian Undescribed genus #1. As a bare arista also occurs in many other Syrphidae, this character is of limited diagnostic value.

Thorax

A pilose postpronotum has been considered to be an important and stable character for distinguishing Microdontinae (as well as Eristalinae) from Syrphinae (Thompson 1969, 1972). In the present study, the postpronotum was found to be pilose in the majority of Microdontinae, but certainly not in all. The postpronotum is bare in several taxa (e.g. Ceriomicrodon petiolatus, Masarygus, Sulcodon, Surimyia, Paramixogaster, Piruwa, Schizoceratomyia). This needs to be taken into account when using keys to genera of Syrphidae in which this character is used (e.g. Thompson 1999).

A few other characters involving the presence or absence of pile on thoracic sclerites have been used. Thompson (1969, 1972) noted that the anterior part of the anepisternum is pilose in Microdontinae, except in Ceriomicrodon petiolatus. In addition, a bare anterior anepisternum was found in an Aristosyrphus sp. n., a Mixogaster sp. n. and in some species of Spheginobaccha. According to Hull (1949) the metasternum is always pilose in Microdontinae. However, this was only true for slightly more than half of the presently studied taxa. The subscutellar hair fringe was absent in all studied Microdontinae (character of Thompson 1969, 1972). This character also applies to several other Syrphidae (Hippa and Ståhls 2005), so it is not by itself group-defining, although it could be useful in keys.

Another thoracic character considered of importance for Microdontinae (Thompson 1969, 1972) is the presence of a complete ‘postmetacoxal bridge’, formed by the connection of the metapleura. As already observed by Cheng and Thompson (2008), this bridge is lacking in Spheginobaccha. The present study revealed that the metapleura are also distinctly separated in certain species of Rhoga (Rhoga maculata, Rhoga mellea, Rhoga sepulchrasilva). In two other taxa (Paramixogaster variegata) and Surimyia) the metapleura seem to be touching only in one point, implying an intermediate state for this character. Among other Syrphidae, a complete postmetacoxal bridge is rare, but it is found in e.g. Baccha elongata (Fabricius, 1775), Neoascia Williston, 1886 and Sphegina Meigen, 1822 (Hippa and Ståhls 2005), and also in Leucopodella Hull, 1949.

The well-developed plumule, a plumose posterior extension of the subalar sclerite, is considered to be an important character of Syrphidae. In most Syrphinae and Eristalinae the plumule is usually strongly developed, except in Ceriana Rafinesque, 1815, Sphiximorpha Rondani, 1850, Neoascia, Sphegina, Eosphaerophoria Frey, 1946, Allograpa ventralis (Miller, 1921) and some species of Ocyptamus (Hippa and Ståhls 2005, Speight 1987, X. Mengual pers. comm.). As noticed by Thompson (1969, 1972), Speight (1987) and Hippa and Ståhls (2005), the plumule is strongly reduced in Microdontinae. This is confirmed by the results of the present study, although considerable variation was found. In a few taxa, the plumula is entirely absent (e.g. Carreramyia, Masarygus, Spheginobaccha), while in others a short plumula can be found, with both the length of this sclerite and the microtrichosity varying in length.

Speight (1987) drew attention to another character: “At the outer ends of the transverse sulcus of the mesoscutum, Microdon possesses a pair of shelf-like, semi-circular, sclerotized outgrowths of the mesoscutum, which do not seem to have an equivalent in other Syrphids”. This apparently indicates the notal wing lamina, which, however, is also well-developed in certain other syrphids besides Microdon, as noted by Hippa and Ståhls (2005). The present data indicate that the notal wing lamina is undeveloped in several Microdontinae, such as Aristosyrphus, Eurypterosyrphus, Masarygus, Paragodon, Rhoga and species of Hypselosyrphus, Indascia and Paramixogaster. A strongly developed notal wing lamina (in the sense of Hippa and Ståhls 2005) was only found in Chrysidimyia. This character has little diagnostic value for the Microdontinae as a subfamily.

As Speight (1987) noticed, the subscutellum (metanotum) is “unusually flat” in Microdon, whereas in many other Syrphidae often a convex plate is present. This character was found to be variable among Microdontinae, but in this group the subscutellum is never as strongly swollen as in several other Syrphidae. However, as many intermediate states occur, this character cannot be used conveniently as diagnostic at the subfamily level.

Wings

The presence of the stigmal crossvein was mentioned as a character of the Microdontinae by Hull (1949) and Thompson (1969). The only exceptions found in the present dataset are Spheginobaccha and Paramicrodon delicatulus Hull, 1937 (the crossvein is present in other studied species of Paramicrodon). A quick but far from exhaustive scan of this character among other Syrphidae learned that the stigmal crossvein is also present in many Eristalinae.

Hull (1949) and Thompson (1969) noted that the apical crossveins M1 and dm-cu are positioned perpendicular to, respectively, vein R4+5 and vein M in most Microdontinae. Exceptions are Aristosyrphus, Mixogaster, Spheginobaccha, and to a lesser extent Kryptopyga and Schizoceratomyia, in which the anterior 1/3 or 1/2 is directed outward. Among other Syrphidae, perpendicular marginal crossveins can be found in e.g. Neoascia and Ocyptamus Macquart, 1834 (subgenus Calostigma Shannon, 1927).

In all Microdontinae, as noticed by Thompson (1969), crossvein r-m is positioned basal of the middle of cell dm. This is not an exclusive character of the subfamily, however, as it is shared with all Syrphinae and many Eristalinae.

An apparently universal character for Microdontinae is the basally curved vein R2+3. The first to introduce this character were Hippa and Ståhls (2005), who noted that the only other Syrphidae in which this character is found are the Cerioidini. No exceptions were found in the present dataset. In the present paper, an attempt is made to describe this important character in a way that makes it easier to judge it objectively (Fig. 435).

Legs

The legs of most Microdontinae are marked with clear scars subbasally at the femora and subapically at the tibia, visible as creases surrounding the legs. These scars are named cicatrices, singular cicatrix (Hull 1949, Thompson 1969). In Microdontinae, this character is usually very pronounced, but a few exceptions were found among the studied taxa (e.g. Masarygus palmipalpus, Piruwa phaecada, Schizoceratomyia flavipes). These taxa are small in body size, and cicatrices are present in taxa which are considered closely related (e.g. Schizoceratomyia barretoi). This suggests that the apparent absence of cicatrices might merely be a matter of reduction or reduced visibility of the character. Vague cicatrices can also be seen in several Syrphinae and Eristalinae, although never as clear as in Microdontinae. With these considerations in mind, the character holds a good ‘indicating value’ for diagnosing the subfamily, but it should be applied with caution.

Speight (1987) found that all Syrphidae except Microdon posess a long, blade-like process projecting outwards from the antero-lateral end of the outer side of the posterior mesocoxite, which he termed “trochanteral process of the mesocoxite”. This character has not been examined in the present study.

Abdomen

In Microdontinae, four preabdominal segments are found in the male, as has been noted by many previous authors (e.g. Thompson 1969, Hippa and Ståhls 2005). This character is shared with the Eristalinae, but constitutes a difference with the Syrphinae. No exceptions were found.

Another abdominal character, noted by Thompson (1969) is the position of the first abdominal spiracle, which is embedded in the metaepimeron in Microdontinae. In the present study, this character was confirmed for most taxa. In a few small taxa the character could not be verified because the spiracle could not be found, neither in the metaepimeron nor in the adjacent membranes. The diagnostic value of this character is limited, as the first abdominal spiracle is also embedded in the metaepimeron in many Syrphinae and Eristalinae (Hippa and Ståhls 2005).

Male genitalia

The last published characterization of genitalia of Microdontinae is the one of Thompson (1969, with some additional notes in 1972). Although since then the understanding of the homologies of Diptera genitalic structures and their terminology has advanced (McAlpine 1981, Sinclair 2000), the characters listed by Thompson (1969) to distinguish Microdontinae from other Syrphidae are still useful. Some of these characters have also been noticed by other authors (Shatalkin 1975a, b, Speight 1987).

Most of the singularities of the genitalia of Microdontinae are found in the hypandrium (9th sternum) and its associated structures. The hypandrium itself is a simple structure in Microdontinae, lacking separate lobes.

In most taxa, the hypandrium seems to consist of a basal part and an apical part. In certain species this distinction is very clear, because the basal part is convex in lateral view (e.g. Figs 24, 363, 396), but in other ones these parts are smoothly fused and one needs to look carefully to distinguish them (e.g. Figs 171, 179, 319). However, distinction is possible in most cases because the apical part is usually less sclerotized than the basal part and it is covered with very fine microtrichia, while on the basal part these are lacking. There is no doubt that the basal part is the actual hypandrium, because it articulates with the epandrium basolaterally. Possibly, the apical part is homologous to the gonopods of other Diptera, which are usually simple in Muscomorpha and more or less absent in Syrphoidea (McAlpine 1981). In most Microdontinae the apical part consists of one single structure. If this structure is homologous to the gonopods indeed, then this would imply that the gonopods have become fused. In a few taxa (with a basal position in the phylogeny presented in Reemer and Ståhls in press), the apical part of the hypandrium consists of two separate lobes, e.g. in Aristosyrphus (incl. Eurypterosyrphus), Mixogaster and Spheginobaccha (Figs 29, 32, 246, 387). In these cases it is easier to imagine that these structures are homologous to gonopods. In only one studied taxon, Menidon falcatus, no apical part of the hypandrium seems to be present.

No postgonites (parameres of McAlpine 1981, superior lobes of Metcalf 1921 and Hippa and Ståhls 2005) can be distinguished in Microdontinae, a rare occasion among Diptera according to McAlpine (1981). Hippa and Ståhls (2005) supposed that in this subfamily the parameres are integrated into the phallus, but did not present evidence for this hypothesis.

The phallus (subdivided by Thompson 1969 into ejaculatory duct and ejaculatory hood) is tubular and elongate. Its structure is simple: no separate structures can be recognized, as is possible in other Syrphidae (basiphallus, distiphallus etc.). In most taxa, the basal part (termed ‘chitinous box’ in Metcalf 1921 and Thompson 1969) is swollen and spherical (e.g. Figs 29, 363, 385, 405), but in a few this is not obviously so (Figs 22, 386). This basal part might be formed out of the phallapodeme, as Thompson (1974) appears to suggest for Spheginobaccha. However, this seems unlikely, because in other Diptera the phallapodeme does not seem to have a sperm-guiding or -collecting function, while in Microdontinae the spherical base of the phallus clearly has an intermediate position between the sperm duct and the apical part of the phallus. Usually, no external lobes are present, but in some taxa a dorsobasal projection was found (Fig. 22). The aedaegus can be unfurcate or bifurcate. Furcate aedeagi can be divided into a number of types, depending on whether the furcation point is basal or apical, and on the length of the ejaculatory processes (see character nos. 163–165 in Reemer and Ståhls in press).

The phallus, or actually the ejaculatory hood, articulates ventrally with the hypandrium and dorsally with the subepandrial sclerites. The point of articulation with the hypandrium is basal, in contrast with all other Syrphidae. The only studied microdontine taxon in which the phallus was observed to articulate apically with the hypandrium is the African taxon Spheginobaccha guttula Dirickx, 1995, a representative of the perialla-group of Thompson (1974).

Except for the studied African species of Spheginobaccha, Spheginobaccha guttula and Spheginobaccha dexioides Hull, 1944, none of the studied Microdontinae has a clearly recognizable phallapodeme. In the Oriental species of Spheginobaccha this structure is also more or less spherical. According to Thompson (1972), the phallapodeme can be absent or “double” in this subfamily. No explanation is given, but judging from a figure of the genitalia of Microdon manitobensis Curran, 1924 in Thompson and Rotheray (1998) and Vockeroth and Thompson (1987), the phallapodeme in the sense of Thompson corresponds with the dark lines named ‘lateral strips’ in Reemer and Ståhls (in press, character no. 171). This seems unlikely, because the phallapodeme is a single structure while the lateral strips are paired.

Thompson (1969, 1972) pointed out that the ejaculatory apodeme of Microdontinae is ‘triangularly flared’ apically, except in Paragodon, in which it is not sclerotized. The present study has revealed no other taxa with an unsclerotized ejaculatory apodeme. The shape of this structure was found to be very variable, ranging from elongate, round, trapezoid, triangular, square to rectangular. The ejaculatory sac was found to be sclerotized in all taxa except Paragodon and Surimyia. This structure is also variable in shape.

No characters useful for diagnostic purposes at subfamily level were found in the epandrium and associated structures. The shapes of the cerci and surstyli are highly variable, so much even that it is difficult to use them at generic level.

Summarizing statement

When the characters of Microdontinae described by previous authors are studied across a large set of taxa, as has been done in the present study, exceptions can be found for almost all of them. Characters for which no or few exceptions were found are listed in Table 2. The character of the basal shape of vein R2+3 seems to be the most exclusive external character to separate the subfamily from other Syrphidae. A key to distinguish Microdontinae from other Syrphidae is given below. As not all Syrphidae have been studied, doubtful cases may occur, so it is recommended to verify at least a few of the other characters in Table 2, preferably those of the male genitalia.

Table 2.

Characters considered to be of good diagnostic value for separating Microdontinae from other Syrphidae, with indication of known exceptions. See text for Discussion.

Character statement State in Microdontinae Exceptions State in other Syrphidae Exceptions
Head
eyes of male, contiguity dichoptic Spheginobaccha chillcotti usually holoptic several
Thorax
postpronotum, pilosity present several, e.g. Masarygus, Surimyia, Paramixogaster Syrphinae: bare<br/> Eristalinae: pilose a few Syrphinae (e.g. Allobaccha Curran, 1928)
postmetacoxal bridge, presence present Rhoga (in part), Spheginobaccha absent e.g. Baccha elongata (Fabricius, 1775), Leucopodella Hull, 1949, Neoascia, Sphegina
plumule, degree of development short or absent none long Cerioidini, Neoascia, Sphegina, Eosphaerophoria Frey, 1946, Allograpta ventralis (Miller, 1921), Ocyptamus Macquart, 1834 in part.
Wing
stigmal crossvein, presence present Paramicrodon delicatulus, Spheginobaccha Syrphinae: absent<br/> Eristalinae: variable unknown
vein R2+3, shape basal part strongly curved (Fig. 435: angle A > angle B) none weakly curved (Fig. 435: angle A < angle B) Cerioidini
Legs
femora and tibiae, presence of subbasal and subdistal cicatrices present Masarygus palmipalpus, Piruwa phaecada, Schizoceratomyia flavipes absent or weakly developed none
Abdomen
abdomen, number of preabdominal segments four none Syrphinae: five, except four in Pipizini<br/> Eristalinae: four none
Male genitalia
postgonites, presence absent none present none
phallus, point of articulation with hypandrium basal Spheginobaccha guttula apical none
phallus, apical part, shape tubular, elongate, without separate structures (often furcate) none rarely elongate, usually with separate structures
phallus, basal part, shape usually spherical Archimicrodon never spherical none
phallapodeme, presence absent Spheginobaccha (African taxa only) present none
Character statement State in Microdontinae Exceptions State in other Syrphidae Exceptions
Head
eyes of male, contiguity dichoptic Spheginobaccha chillcotti usually holoptic several
Thorax
postpronotum, pilosity present several, e.g. Masarygus, Surimyia, Paramixogaster Syrphinae: bare<br/> Eristalinae: pilose a few Syrphinae (e.g. Allobaccha Curran, 1928)
postmetacoxal bridge, presence present Rhoga (in part), Spheginobaccha absent e.g. Baccha elongata (Fabricius, 1775), Leucopodella Hull, 1949, Neoascia, Sphegina
plumule, degree of development short or absent none long Cerioidini, Neoascia, Sphegina, Eosphaerophoria Frey, 1946, Allograpta ventralis (Miller, 1921),