HOW TO KNOW THE IMMATURE INSECTS 



44b. Movable 10th abdomincd segment present be- 

 low 9th abdominal tergimi. Fig. 223 47 



45 a. Body cylindrical, without ventral gills 46 



Fig. 222. Tip 

 of abdomen. 



45b. Body flat, broadly oval; with ventral gills freely exposed from 

 2nd to 6th abdominal segments. 

 Fig. 224 Family PSEPHENIDAE 



The larvae are aquatic and attach to 

 stones in swift-flowing streams, rapids, 

 cascades and waterfalls. They are flat- 

 0,j^^s tened and disc-like. Their pupae ore sub- 

 merged and firmly attached to stones. 



Fig. 224. Psephenus le- 

 contei Lee. 



46a. Antennae comparatively long; 10th abdominal segment with a pair 

 of large lobes usually carrying spinose diverticles. 

 Fig. 225 Subfamily Ptilodactylinae, HELODIDAE 



The biology of this subfamily 

 needs to be investigated. The larvae 

 of Ptilodactyla seTricollis Say are found 

 , in the damp soil of forests. Only a 

 few species are known in North 

 America. Some systematists believe 

 that this subfamily belongs else- 

 where or as a separate family. 



Ptilodactyla serri- 



9th and 10th ab- 



dominal segments. 



92 



