AQUATIC INSECTS 



hairs, and at the end of the abdomen there is a similar but 

 unjointed gill. 



The larvas are predacious upon caddis worms and upon one 

 another. They do not come out of their hiding places until 

 they are ready to pupate, when they clamber out on land 

 and seek another hiding place or burrow in the moist earth. 



Dobson-fly, Corydalis comuta. — The larvae of Corydalis 

 cornuta (Fig. 185, i), commonly known as crawlers, hell- 

 grammites, and bass bait, live under stones in the swiftest part 

 of rapid streams (PI. I). They are fiercely predacious insects, 

 and will seize upon mayflies and stoneflies as soon as they are 

 put in the same collecting dish with them. 



When fullgrown they are 2 or 3 inches long with dark brown, 

 rough looking skin, and large jaws which they extend lustily 

 at the slightest irritation (Fig. 185). Their bodies are 



Fig. 185. — Dobson-fly, Corydalis cornuta: i, larva; 

 2, head of adult male; 3, adult female. 



243 



