534 MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
KEY TO FAMILIES—Continued 
LARVAE—Continued 
8. Abdominal segments 1 to 6 subdivided; posterior spiracles situated 
upon antepenultimate segment 
Omphrolidae (Scenopinidae,) p. 535, Therevidae, p. 535. 
Abdominal segments usually simple; posterior spiracles situated 
upon the penultimate segment; thoracic segments each with 
2 long hairs, one on each side; apical segment with 6 or 8 long 
hairs; body straichtaimiliie = a eee Asilidae, p. 534. 
Faminty ASILIDAE 
Robber Flies 
The Asilidae (fig. 145) are moderate- to large-sized, thickly haired 
flies with tapering abdomen, depressed vertex, and piercing proboscis. 
The eyes are always separated, and the legs are strong. with stout 
FIGURE 145.—Robber fly, Asilus sericeus Say; A, Adult fly; B, puparia; C, larva. 
About X2. 
claws. The larvae are cylindrical and have a thick skin often girdled 
with protuberances or abdominal processes for locomotion. <As a rule 
the sharply differentiated posterior spiracular segment is characteristic 
for most species of the family. The larva of Laphria have the first six 
abdominal segments subdivided, the anterior portion of each being 
furnished with six wartlike retractile protuberances. t 
Most of the larvae are predaceous. Aszlus notatus (Wied.) and f 
Leptogaster flavipes Loew have been taken from decaying wood in : 
association with tenebrionid and cerambycid larvae: Diogmites and 
Laphria spp. from decaying wood infested with coleopterous larvae; {> 
and L. indew McAtee, L. flavicollis (Say), and L. thoracia (F.) from 
beetle-infested hickory wood. Other species belonging S several 
genera live in the soil and are predaceous on white orubs. 
