TRICHOPTERA 



561 



do not build cases, but crawl about naked beneath stones seeking their 

 food ; they feed on small larvae 

 and filamentous algas. The 

 larva of our most common 

 species, Rhyacophila fuscula, 

 when full-grown enters a crev- 

 ice between two large stones 

 and builds a wall of pebbles 

 about itself; this wall is ce- 

 mented in place with silk; 

 and the chamber thus inclosed 

 is much larger than the insect 

 (Fig. 689); it then spins a 

 parchment-like cocoon about 

 its body, within which it trans- 

 forms. The making of a co- 

 coon is a family characteris- „. ^„ ^ , ^ „, ,, ., , ., ,. 

 tic of the RhvamnhiliH-P-onlv ^^^' 689-— A larva of Rhyacophila building 

 nc 01 tne Knyacopnnidae , only ^^g ^^^^^ chamber, exposed by lifting off 

 afewothercaddice-wormsspm the stone beneath which it was. (From 

 cocoons. Needham and Lloyd.) 



The members of the subfamily Glossosmatina^ build cases out of 

 sand or small stones. Our best- 

 known species is Glossosdma anieri- 

 cdna, the habits of which are de- 

 scribed by Lloyd. Figure 690 repre- 

 sents a dorsal and a ventral view of 

 the case. The larvae live singly on 

 the stones of the stream's bottom; 

 but before pupating they congre- 

 gate in dense colonies on the sides 

 and bottoms of stones, with their 

 cases placed edge to edge, sometimes 

 one on top of another. At this time 

 the floor of the case is cut away and 

 the rim of the cup-like roof is glued to the supporting rock. 



Fig. 690. — Case of Glossosonta ameri- 

 cana: a, dorsal view; b, ventral 

 view. (After Lloyd.) 



Family HYDROPTILID^ 



The Micro-Caddice-Flies 



This family is composed of minute caddice-flies, which resemble 

 tineid moths in appearance. The larv^ are found in both quiet water 

 and rapid streams, and often occur in very great numbers. They 

 build cases which differ in form in the different species, but are usually 

 fiat; some are elliptical, some flask-like, and others kidney-shaped; 

 all are open at both ends; they are much larger than the larvce. 

 They are usually composed entirely of silk ; but in some species grains 

 ni sand or minute bits of vegetable matter are used. "Agraylea 



