THE PHRYGANID^E. 47 



overhanging trees and bushes, to which they 

 adhere till they are hatched a process which, 

 in summer weather, soon takes place. The 

 eggs produce little six-legged larvae, which fall 

 into the water, and immediately set about 

 constructing for themselves tube-like cases in 

 which to reside secure from their numerous 

 enemies in the list of which are other larvae 

 and fishes. When seen at the bottom of the 

 water these cases appear like short bits of stick, 

 but they will be found, on examination, to be 

 regularly and beautifully constructed of various 

 materials some of minute portions of the leaves 

 and other parts of aquatic plants ; others of pieces 

 of reed, grass, and the like; and many of fine 

 gravel, sand, and even little shell fish, each 

 species selecting its peculiar materials, which are 

 neatly and strongly cemented together with a kind 

 of glue, which the larvae produce, and which com- 

 pletely resists the action of water. The cases are 

 lined inside with a kind of silk, which the insect 

 spins from its mouth in the same manner that ca- 

 terpillars do. The cases of most species being 

 specifically lighter than water, the larvae swim 

 with facility, and thus have a greater range for 

 their food than those species which inhabit cases 

 composed of denser materials. These last are 



