m. Posterior crossvein (m-cu) wanting; wings smoky or with clouds. Europe. G. pecorum
mm. Posterior crossvein (m-cu) present, at least in part.
n. Wing hyaline with smoky median cross band, and two or three spots; posterior trochanters with hook in the male and a prominence in the female. World wide distribution. G. equi.
nn. Wings without spots.
o. Posterior crossvein (m-cu) distad of the anterior crossvein (r-m); legs, particularly the femora, blackish brown. Europe and North America. G. hæmorrhoidalis
oo. Posterior crossvein opposite or proximad of the anterior crossvein. Europe and North America. G. nasalis
ll. The costal vein ends at the tip of M1+2, M1+2 with a bend, the cell R5 hence much narrowed in the margin, or closed.
m. Proboscis geniculate, inserted in a deep slit; female without extricate ovipositor; arista either bare or plumose; squamæ large; facial grooves approximated below.
n. Arista bare, short. Larvæ in rodents. Tropic America. B. princeps. Bogeria Austen
nn. Arista pectinate above.