Nerve-winged Insects; Scorpion-flies; Caddis-flies 227 



flows swiftest. They are carnivorous, feeding upon the nymphs of stone- 

 flies, May-flies, and other insects. When about two years and eleven months 



,l.md 



m. 



FlG. 313. Head of larva, pupa, and adult of dobson-fly, Corydalis cornuta, showing 

 development of the mouth-parts of the adult within the mouth-parts of the larva. 

 A, head of a larva with its cuticle dissected away on the right-hand side, revealing 

 the pupal parts; B, head of male pupa with cuticle dissected away on right-hand 

 side, revealing developing imaginal parts; C, head of female pupa with cuticle 

 wholly removed, showing imaginal parts; D, head of adult male, md., mandible; 

 mx., maxilla; li., labium; lb., labrum; ant., antenna; l.h., larval head-wall; p.h., 

 pupal head-wall; ga., galea; H.p., labial palpus; mx.p., maxillary palpus. Any 

 of these terms may be prefixed by/, larva; p, pupa; or i, imago. 



old the larva leaves the water, and makes a cell under a stone or some other 

 object on or near the bank of the stream. This occurs during the early 



