Microdon Meigen

Reemer, Menno & Stahls, Gunilla, 2013, Generic revision and species classification of the Microdontinae (Diptera, Syrphidae), ZooKeys 288, pp. 1-213 : 44-45

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 in Microdon 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.