Mixogaster

Mixogaster is a genus of hoverflies native to North America and South America, with 21 known species. Mixogaster is distinct by lacking an appendix on vein R4+5, having a reduced and bare metasternum, an unarmed scutellum, and usually an appendix on vein M extending in cell R4+5. Larvae are found in ant nests.

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.

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