NATURE'S CRAFTSMEN 



There are, however, many families of insects with 

 whom this quaUty is reversed. The architectural in- 

 stinct is inborn with the larva) and is wanting or qui- 

 escent in adults. While the former give some rare ex- 

 amples of skill in sheltering and caring for themselves, 

 the latter live uninteresting lives, except in the maternal 

 act of perpetuating their species, which for a brief 

 period excites the female to interesting activity ere the 

 spark of life expires. As the larvae of these insects are 



solitary, and nature 

 thrusts upon them re- 

 sponsibility for their 

 own nurture and pres- 

 ervation, the posses- 

 sion of an adequate 

 instinct is essential. 

 It is the purpose of 

 this chapter to give a 

 record, with illustra- 

 tions, of that instinct 

 as shown in the life 

 of a single example 

 of one of these spe- 

 cies—the net-making 

 caddis worm. 



There are few fa- 

 miliars of American 

 and English fresh- 

 water streams who do not know something of the 

 case -making caddis worm. It has the curious habit 

 of covering the silken case in which it encloses its soft 

 body with minute pebbles, or grains of sand and tiny 

 shells, or bits of grass and leaves. Thus clad, it walks 



272 



CASE-MAKING CADDIS WORMS 



