13<S NOTJTII AMERICAN DIPTEKA. 



1. Last abdominal segment free, broadly attached 2 



Last abdominal segment (twelfth) retractile within the preceding, small 



and distinctly constricted. ....... 7 



2. Larvae with two pairs of chitinized jaws, that is with two outer moutli- 



hooklets, and two inner, straight, triangular points (Horses). 



GaSTKOI'IIILUS. 



Larvaj with two or no mouthliooklcts. ...... 3 



3. Larvie on the median segments with dorsal, spindle-shaped tubercles; 



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



Larvae without sucli tubercles ; one pair or no mouth-hooklets present. 5 



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



low (Sheep). ......... (EsTRLS. 



Antennae appro.ximated or contiguous; body elongated, somewhat 

 broader in front than behind (Deer). . . . Cici-iienomyia. 



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



Two small mouth-hooklets present (Rodents). . . CEstuomyia. 



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

 Bristles stronger below than above (O.x, etc;.) . . Hypodeema. 



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



Larvaj club-shaped, more slender posteriorly (i\rtiodactyls, Carnivora, 



Primates). ......... DEitMAToniA. 



54. SARCOPHAGID.E. 



Usually thick-set, moderately large to rather small flies. 

 Front in both sexes broad, though usually somewhat narrower 

 in the male. Arista of the antennse plumose to the middle or 

 a little beyond, the distal ])ortion bare ; this last character 

 alone is the ultimate distinctive one of the group. Abdomen 

 composed of four visible segments, with the macrochaetaB 

 ustially confined to tlie distal })ortion, though sometimes occtir- 

 ring on the margin of the second and following segments and 

 very rarely on the disk ; male hypopygium often prominent. 

 First posterior cell of the wings always much narrowed or 

 closed. 



This family of flesh-flies, as they are often called, though 



