CADDIS-WORMS 



261 



useful only at the time when the fly is about to 

 emerge, and that they serve chiefly or solely to break 



D 



Fig. 83. — Pupa of Hydropsychid Caddis-worm. A, case of small stones, seen from 

 attached side, with enclosed pupa ; B, larva within case, preparing to pupate ; 

 C, pupa ; D, pupal head, showing large hooks (mandibles). 



down the gritty partition which closes the sheath. 

 Vallisnieri has seen in the end of June pupai which 



