200 INSECT ARTIZANS AND THEIR WORK 



stream wide enough and deep enough to admit its 

 case, which it then up-ends and allows to sink into 

 the pit until stopped by the larger stones recently- 

 added to the other end. It now resumes its former 

 position in the case and changes into the chrysalis. 

 Its case is now a vertical tower, fixed by the weight 

 of its upper end. The pupae escape from their 

 cases before undergoing the final change into 

 Caddis Flies ; and whilst some species emerge from 

 the chrysalis at the surface of the water, others first 

 make their way to land. 



Among the allies of the Caddis which turn their 

 clothes into fixed residences by attaching them to 

 stones, etc., are several species of the Hydropsychides. 

 One of these, Rbyacophylax, which MSller found 

 in the rapids of Brazilian rivulets, in addition to its 

 suit of clothes, or house, proper, builds a funnel- 

 shaped verandah to it. The verandah is covered 

 with a delicate network of silk. Now the house is 

 always built with its door looking up stream, so 

 that as the current flows through the network of 

 the verandah anything suitable for food is strained 

 out and falls handy to the mouth of Rbyacophylax. 

 Somewhat similar is the device of a North American 

 species of Hydropsyche, which attaches the widest 

 circumference of its net to bits of twig and the 

 stems of water weeds. These two are entitled to 

 be classed as Trappers as well as Tailors. 



We have already described the way in which 

 the caterpillars of the Coleophorid moths, beginning 

 life as leaf-miners, make for themselves portable 



