160 MISC. PUBLICATION 631, U. S. DEPT. OF AGRICULTURE 



are vestigial. The costa is without fractures on its basal half; the 

 subcosta is distinct. The abdomen is cylindrical, somewhat elongated, 

 usually narrowed at its base. A useful character which will dis- 

 tinguish members of this family from all Acalypteratae other than 

 the very dissimilar Kopalomeridae is the presence on the rim of the 

 posterior spiracle of one or more bristlelike hairs ; these are best seen 

 under at least a moderate magnification. 



The adults are common around excrement and decaying vegetation ; 

 the larvae are scavengers. 



The Genus SEPSIS Fallen 



In this genus the front is without bristles, but there are two pairs 

 of verticals; the first and second basal cells are separated; and the 



Figure 96. — Sepsis violacea, adult female. 



anterior femora, though they may bear coarse spines, are never pro- 

 vided with a row of close-set spinules ventrally. 



Pathogenesis. — The larvae breed chiefly in excrement, including 

 that of man ; however, they may occur in decaying food. 



The Family PHORIDAE 



This family includes a number of small hump-backed flies of a char- 

 acteristic appearance and, in the winged forms, with a very distinctive 

 venation. The front is wide and usually bears a number of well- 

 developed bristles. The antennae have three segments, the third 

 segment being very large and tending to obscure the small basal two ; 

 the arista may be dorsal or apical. The wing venation consists of two 



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