AQUATIC INSECTS 



times they are separated from the lily pad, sometimes moored 

 to it by a strand of the torn tissue. They are filled with water 

 but the larvae can breathe by means of bushy branched gills 

 extending from the sides of the body. They feed upon the 

 leafy walls of their cases, first upon the inner layer and when 

 they are older, upon the shiny outside. 



In this, as in other species, there appear to be two broods 

 of caterpillars; the first one makes the full-sized cases common 

 in June and July. These pupate within leaf-cases also usually 

 beneath a lily pad, and the adults which fly about over the 

 lily ponds have mouse-gray front wings and white hind ones 

 (Fig. 200). Soon another generation arises, the caterpillars 

 of which sink down through the water in autumn and hiber- 

 nate among the water-sodden leaves of the lily plant. Com- 

 mon and generally distributed. 



Fig. 201. — I, Lily-leaf caterpillar, Nymphula 

 obliterans; and 2, its floating leaf-case; 3^ moth. 



Lily-leaf caterpillar, Nymphula obliteralis. — In the southern 

 states it is a pest upon water-lilies. These caterpillars (Fig. 

 201) make their cases, about one half inch long, of the leaves 

 of water-lilies and pondweeds. They have no gills and are 

 entirely dependent upon the bubble of air which surrounds 

 them in their leaf-cases. The male moths are dull black 

 with obscure markings of yellow and white; the females are 

 browner and of larger size. 



259 



