The, Caddis Flies 



from either orifice. When ready to transform to the adult stage 

 the pupa works its way through the guarded orifice, swims to 

 the surface of the water, and crawls out, where possible upon a 

 twig or other vegetation, or upon the bank. It may cast its 

 pupal skin while still in the water, the wings remaining unex- 

 panded, but as soon as it leaves the water the wings expand 

 instantly to their full size, and the fly departs through the air. 

 This statement is based upon an interesting observation by Corn- 

 stock, who states that the instant expansion of the wings is 

 necessitated by the fact that the insects studied by him normally 

 emerge from rapidly flowing streams, which dash over rocks, 

 and if much time were required in this wing-expansion, the 

 water would destroy the wings for purposes of flight, and dash 

 the insect down. The larval food of the caddis flies is mainly 

 vegetable, but there is one group which is carnivorous. The 

 order is not a very large one, but more than one hundred and 

 fifty North American species have been described. 



As common as are the caddis worms, and as often as they 

 have been watched in streams and in aquaria, not a single full 

 life history has been recorded in this country, and a fascinating 

 field for original investigation is therefore open to the first comer. 



Table of Families 



Spines on the legs, three ocelli i 



No spines, only hairs and spurs 2 



1 — Four spurs on middle tibiae Family Phryganeidce 



Two or three spurs on middle tibiae Family Limnephilidce 



2 — Last two joints of palpi not elongated, simple not flexible. . .3 



Last joint of palpi, elongate, flexible, palpi hairy 5 



3 — Male palpi four-jointed, ocelli absent 4 



Male palpi five-jointed, ocelli often present, when absent the 



spurs 2-4-4 Family Rhyacophilidce 



4 — No spurs on anterior legs Family Hydroptilidce 



Spurs present on anterior legs Family Sericostomatidce 



5 — Basal joint of antenna long and large, wings slender, no 



ocelli Family Leptocerida 



Basal joint of antenna shorter, wings broader, last joint of 



palpi multi-articulate Family Hydropsychidce 



197 



