258 NATURE STUDY AND LIFE 



instead of remaining spread out, are folded over the back 

 while at rest. They are the delicate, shimmering, scintil- 

 lating insects that we so often see flitting and darting 

 about the borders of ponds and streams. The larvae are 

 aquatic, and the life story in general is like that of the 

 dragon flies. The French call them demoiselles. 



Caddis Flies. " Will you please tell us what these things 

 are ? Teacher does n't know nor any one else in our 

 school. They are alive." The speaker was one of a half- 

 dozen boys ; he had a tin can in one hand and held out 

 some small objects in the other. "Those are caddis fly 

 worms," I answered. "What do they eat?" was his next 

 question. I told him that they fed upon water plants, 

 and said that if they would keep them in an aquarium with 

 plenty of plants, they might see one pop out of the water 

 and change like a flash into a four-winged fly. 1 



More than 150 different kinds of caddis flies have 

 been described for North America. Most of them are 

 vegetable feeders and build cases of tough silk, with 

 all sorts of materials, grains of sand, small stones, bits 

 of wood, pine needles, snail shells, etc., woven into their 

 walls; so that their occupants are pretty well protected 

 from predaceous insects and even from fishes. Generally 

 the case is free, and the larva drags it about as it seeks its 

 food. In swiftly flowing streams, however, the cases are 

 often fastened to the rocks. In one family of caddis flies 

 the larvae are carnivorous, and these construct funnel- 

 shaped silken nets attached to stones, the small end of the 



1 I learned that the boys had " fixed up " one of the chicken coops in 

 the neighborhood into what they called their "laboratory" and were spend- 

 ing their summer vacation " studying insects and all kinds of things." 



