o. Tarsi broadened and flattened, hairy, anal lobe of the wing large. Larvæ in rodents. A number of American species. Cuterebra.
oo. Tarsi slender, not hairy; anal lobe of the wing moderate. Larvæ in man and other mammals. Tropic America. D. cyaniventris. Dermatobia Br.
mm. Mouth parts very small, vestigial; arista bare.
n. Facial grooves approximated below, leaving a narrow median depression or groove.
o. Cell R5 closed and petiolate, body nearly bare. Larvæ in the nasal cavities of the smaller Ungulates. The sheep bot fly. O. ovis. Widely distributed Oestrus L.
oo. Cell R5 narrowly open, body hairy. Larvæ parasitic on deer. Europe and America. Cephenomyia Latr.
nn. Facial grooves far apart, enclosing between them a broad shield-shaped surface; squamæ large; female with elongate ovipositor. Larvæ hypodermatic on Ungulates. Hypoderma Clark
o. Palpi wanting; tibiæ thickened in the middle.
p. Hair at apex of the abdomen yellow; legs including femora yellowish brown. H. diana
pp. Hair at the apex of the abdomen reddish yellow. Europe and America.