Facial grooves remote, enclosing between them a broad, gently 

 arcuate, shield-shaped surface ; squamae large; female with 

 elongate ovipositor; larvae hypodermatic. ... 5 



4. First posterior cell closed and petiolate; body nearly bare. CEstrus 

 First posterior cell narrowly open; body pilose. Cephenomyia. 



5. Palpi wanting Hypoderma. 



Palpi small, globular. ...... CEdamagena. 



6. Arista bare, short and stout; wings without stump at angle of 



fourth vein. ........ Bogeria. 



Arista pectinate above. ........ 7 



7. Tarsi broad and flattened, hirsute (3, 4, 5); alulae large. 



Cuterebra. 



Tarsi slender, not hirsute; third joint of antennae more elongate; 

 front prominent anteriorly; alulae of moderate size (6, 7). 



Dermatobia. 



1. Last abdominal segment free, broadly attached. ... 2 

 Last abdominal segment (twelfth) retractile within the preceding, 



small and distinctly constricted. ..... 7 



2. Larvie with two pairs of chitinized jaws; that is with two outer 



mouth-hooklets, and two inner, straight, triangular points 

 ( Horses) ........ Gastrophilus. 



Larvae with two or no mouth-hooklets. ..... 3 



3. Larvae on the median segments with dorsal, spindle-shaped tuber- 



cles; one pair of mouth-hooklets present. . . .4 



Larvae without such tubercles; one pair or no mouth-hooklets pres- 

 ent. 5 



4. Antennae broadly separated; body oval, strongly convex above, flat 



below (Sheep) Oestrus. 



Antennae approximated or contiguous; body elongated, somewhat 

 broader in front than behind (Deer) . . Cephenomyia. 



5. No mouth-hooklets. . ....... 6 



Two small mouth-hooklets present (Rodents). Oestromyia 



6. Bristly covering alike above and below (Reindeer) . Osdamagena. 

 Bristles stronger below than above (Ox, etc.) Hypoderma. 



7. Larvae oval (Rodents, Marsupials) .... Cuterebra. 

 Larvae club-shaped, more slender posteriorly (Artiodactyls, Carni- 



vora. Primates). Dermatobia 



