^ 



AQUATIC INSECTS 



on the brook bottom until they are fiillgrown and ready to 

 pupate and then they congregate upon the sides of stones 

 with their cases placed edge to edge. Each larva cuts away 

 the old floor of its case and fastens the rim which is left to 

 the rock. Under this protecting canopy it spins its pupal 

 cocoon. Larvae, pupse, and adults are found all summer. 

 Length of case, little less than one half inch. 



Net-spinning caddis worms, Family Hydropsychidae. — This 

 family is represented in almost every shallow stony brook by 

 hundreds of HydropsycJie larvae and their nets. 



Fig. 192. — Net-spinning caddis worm, Hydro- 

 psyche (Macronema) ; for net see PI. XVI. Width of 

 cup, one half inch or less. 



Hydropsyche (Macronema). — The cup-shaped nets of Hy- 

 dropsyche are built in crevices or on the edges of rocks in 

 waterfalls and riffles (PL XVI). The cup always opens 

 upstream and the larva lies in a loosely woven tube close at 

 the side, whence it can easily reach the food which the water 



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