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 
Fig. 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; li.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 
