80 ELEMENTARY LESSONS ON INSECTS 



find these shelters commonly on the underside of submerged 

 stones and may get the living pupae from them by picking 

 away the pebbles and carefully opening the cocoon with a 

 forceps. When the outer part of the cover is removed one 

 may see through the transparent silken lining of the shelter 

 that the pupa is not wholly inactive. Its body undulates 

 regularly, in such a way as to drive a current of water back- 

 ward through its case. The pupa also breathes by means 

 of gills. Its middle legs are provided with marginal fringes 

 of hairs, adapting them for swimming. It possesses big 

 mandibles, with which at the last it cuts a hole in the end 

 of its case. Then it comes out, and swims to the surface of 

 the water, and molts the pupal skin, and steps out into the 

 air as an adult caddisfly. 



LESSON 7 



Caddisflies 



WORK PROGRAM 



1. Collect adult caddisflies at lights at night. 



2. If dried specimens are to be used, give them a stay over 

 night in a relaxing jar. 



3. Collect larvae and pupae of the net-maker (Hydro- 

 psyche) from the riffles in streams (see p. 183). 



4. Collect different kinds of caddisworms in portable cases 

 from ponds (see p. 182). 



5. Set up a net trough (Fig. 70) with running water; put in 



