1 Proboscis long and slender; labellum sclerotized, without pseudotracheae; Rs variable; abdomen pruinose.............................................................................................................................. 2
Proboscis short; labellum membranous bearing pseudotracheae; Rs short; abdomen shiny.... 6
2 Face short, eyes broadly dichoptic on face; Rs variable............................................................ 3
Face long and linear or eyes holoptic on face; Rs short.............................................................. 5
3 Rs long, arising before middle of basal cells (br and bm); frons flattened; flagellum short, rounded ovate, with subdorsal arista; postcranium concave with conspicuous postocelar sclerite; male terminalia symmetrical ....................................................................... Syneches Walker
Rs short, beyond middle of basal cells; frons convex; flagellum pointed ovate, with apical arista; postcranium convex, without postocellar sclerite; male terminalia asymmetrical......... 4
4 Distal section of R 1 faint, sinuous, running parallel to the Costa; two pair of ocellar bristles; occipital bristles slender; 1 dc posterior bristle long; fore and mid tarsomere 1 without dorsal bristles; dorsal ejaculatory apodeme reduced...................................................... Hybos Meigen
Distal section of R 1 normal; one pair of ocellar bristles; occipital bristles spinelike; posterior dc bristle lacking; fore and mid tarsomere 1 with long dorsal bristles; dorsal ejaculatory apodeme developed ........................................................................................ Smithybos AleRocha
5 Basal section of M and Sc weak or lacking; Rs with apex arched to meet R 1 at right angle; wing with nude areas, without microtrichias; hind femur slender; hind tarsomere 1 short and thickened ................................................................................................................................ Syndyas Loew
M strong basally and Sc present; Rs with apex arched to meet R 1 at acute angle; wing entirely clothed with microtrichias; hind femur thickened; hind tarsomere 1 long and slender.................................................................................................................................. Lactistomyia Melander
6 Eyes distinctly dichoptic on face, rarely holoptic; wing narrow; anal lobe narrow, with rounded margin; R 4 + 5 and M 1 parallel, somewhat convergent; dc and acr with reduced number of bristles, arranged in discrete series on prescutellar disc; male eighth abdominal segment not rotated; hypandrial arms forming narrow, sclerotized dorsal bridge around phallus; hypandrium wider in the middle; Tg 8 of female with a single sclerotized plate............. Neohybos gen. nov.
Eyes holoptic on face, sometimes narrowly dichoptic; wing and anal lobe broad, rarely narrow; anal lobe triangular; R 4 + 5 and M 1 convergent; dc and acr with numerous and disordered bristles on prescutellar disc; male eighth abdominal segment rotated 45 ° to right; hypandrial arms prolonged distally forming membranous chamber dorsolaterally; hypandrium narrowed medially; Tg 8 of female divided in three plates........................................................................................ 7
7 Flagellum narrow, oval or conical; antennae inserted near middle of head; thorax strongly arched; pronotum elongate; mid tarsomere 1 with PV subbasal bristle long; fore and mid tarsomere 1 with long dorsal bristles................................................................ Euhybus Coquillett
Flagellum broad, strongly arched dorsally; antennae inserted high on head; thorax not strongly arched, almost flattened dorsally; pronotum short; PV subbasal bristle of mid tarsomere 1 absent or reduced; fore and mid tarsomere 1 without dorsal bristles............ Cerathybos Bezzi