HOW TO KNOW THE IMMATURE INSECTS 



26a. Head without strong thorns; abdomen with 3 to 4 distinct pairs 

 of spiracles and without spinose armature. 

 Fig. 575 Family CYRTIDAE 



Pupation takes place in web, or bur- 

 row, or under some other objects near 

 the place where the host died. 



Fig. 575. Ogcodes costatus 

 Loew. 



26b. Head usually with strong thorns, at least with elevated ridge- 

 like antennal sheath and several small carinated elevations; ab- 

 domen with 7 pairs of spiracles and spinose armature 27 



27a. Head with 2 thorns. 



27b. Head with more than 2 thorns or with several short tubercles.. .29 



28a. Abdomen with a single transverse series oi spines on each dorsal 

 segment; wing with a long thorn at base. 

 Fig. 576 Family THEREVIDAE 



Fig. 576. Psilo- 

 cephala haem- 

 orrhoidalis Mac- 

 quart. 



The pupae are free and the pupation takes place 

 in the soil. 



The adults of this small family are known as stil- 

 leto flies. The larvae are apparently predacious. 



/ 28b. Abdomen with 2 transverse series oi spines on each dorsal seg- 

 ment; wings without thorns at base Family SCENOPINIDAE 



Little is known about the biology of the pupae. 



208 



