V CADDIS-WORMS 259 



Larva makes silken channels on the surface of stones, which 

 become covered with slime, but prepares firmer cases before 

 pupation. Streams and springs. Tinodes. 



Cases of small stones. Pupa enclosed in a brown cocoon, 

 instead of lying free within the case. Torrents. Rhyaco- 



philidcE. 



Cases of silk, movable, with foreign bodies attached, resem- 

 bling small seeds, slit at each end, at either of which the larva 

 can protrude its head. Sometimes moored by threads. Fixed by 

 strong threads before pupation. Standing or running water. 

 Fam. Hydroptilida. 



I now resume Reaumur's account. " It is not only 

 in the manufacture of their sheaths that these larv^ae 

 exhibit industry. They have subsequently to be 

 transformed into pupae in order to emerge as winged 

 Insects. The pupa is no better fitted to defend itself 

 against the attacks of its enemies than the chrysalis 

 of a Moth. Carnivorous Insects abound in the water 

 as on land or in the air. Accordingly the Caddis- 

 worm, before undergoing its transformation, provides 

 for its safety during the time when it can no longer 

 defend itself. It does not, however, quit its sheath, 

 but closes up the two ends with plates composed 

 of silk or of some other material. In its pupal con- 

 dition it continues to breathe air dissolved in water ; 

 to secure a constant supply of fresh water, the plate 

 which closes each end of the sheath is pierced with 

 holes like a strainer or grating, made of coarse threads 

 of silk. Thus the pupa is furnished with an ample 

 supply of fresh water, flowing through its sheath, 

 while it is sufficiently protected against carnivorous 

 Insects. 



"The pupae may be found in their cases in May 

 and June, but there arc probably some which pass the 



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