96 THE BLOWFLIES oF NortTH AMERICA 
anterior half, the bristles in a short tuft; greater ampulla strong- 
ly reniform posteriorly; intrapostsupraalar bristles absent; 
scutellum usually without apical bristles. 
Legs of medium length; fore tibia with several short antero- 
dorsal bristles; middle femur with a posteroventral row or 
partial row of bristles; middle tibia with one ventral bristle; 
hind tibia with a dorsal bristle near apex; tarsi with claws and 
pulvilli as long as or just slightly shorter than last tarsal seg- 
ment. 
Wing without costal spine; remigium ciliate above posteriorly 
at base; only third vein setulose; anterior cross vein at or near 
middle of second section of fourth vein; posterior cross vein 
sinuate to doubly arcuate; fifth vein with last section one-fifth 
to one-sixth the length of preceding section; sixth vein usually 
short. 
Abdomen with ventral membrane exposed in female; discal 
and median marginal bristles absent on intermediate segments. 
Male genital segments small, nearly ventral and often almost 
hidden. 
Larva. Second instar with oral hooks enlarged near tips. Pos- 
terior spiracle of third instar with incomplete ring or peritreme, 
the ‘‘button’’ absent or poorly defined and situated in the gap 
of peritreme. 
KEY TO GENERA AND SPECIES OF NORTH AM ae 
CHRYSOMYINAE 
1. Hind coxa aildes poeenneye one presupraalar bristle. Lar- 
va eel Senate EE in postspiracular plate. . 
Cow 2h peed O7. gee say wis EEO A ES Gat Chrysomyini 9 
Hind coxa thon fine hair or pile posteriorly; two presu- 
praalar bristles (except in Phormia). Larva with definite 
‘“button’’ in postspiracular plate......:.Phormiini. 13 
2. Parafaciale bare; preintraalar bristles two; predorsocentral 
bristles two or three; back of head concave in profile; 
sternopleural bristles, except occasionally, two; postdorso- 
central bristles three or four, only the prescutellar 
large és jaime a+ eile bib det oi. eee 3 
Parafaciale setose; preintraalar bristles and predorsocen- 
tral bristles absent; back of head in profile protuberant, 
flattened, or but slightly concave; sternopleural bristles 
three; postdorsocentral bristles two or three.......... 8 
