Generic revision and species classification of the Microdontinae (Diptera, Syrphidae) Author Reemer, Menno Author Stahls, Gunilla text ZooKeys 2013 288 1 213 http://dx.doi.org/10.3897/zookeys.288.4095 journal article http://dx.doi.org/10.3897/zookeys.288.4095 1313-2970-288-1 Peradon Reemer gen. n. Figs 291-298 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 Stahls (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.