21 8 Aquatic Organisms 



Caddis-fly pupa? are likewise aquatic (and this is 

 characteristic of no other order of insects) , and like the 

 larvae, they often bear filamentous gills along the sides 

 of the abdomen. They are equipped with huge mandi- 

 bles that are supposed to be of use in cutting a way out 

 through the silk just before transformation. The 

 mandibles are shed at this time. The adult caddis-flies 

 are destitute of jaws and are not known to feed; so 

 they are probably short-lived. 



FIG. 126. Eggs of Triasnodes. 



The eggs of caddis-flies usually are laid in clumps of 

 gelatine. Sometimes they are arranged in a flat spiral, 

 as in Triaenodes, shown in the accompanying figure: 

 sometimes they are suspended from twigs in a ring-like 

 loop, as in Phryganea. Oftener they form an irregular 

 clump. They are usually of a bright greenish color, 

 but those of the net spinning Hy dropsy ches, laid on 

 submerged stones in close patches with little gelatine, 

 are tinged with a brick-red color. 



The moths (order Lepidoptera) are nearly all terres- 

 trial. Out of this great order of insects only a few 

 members of one small family (Pyralidae) have entered 

 the water to live. These live as larvae for the most part 

 upon plants like water lilies and pond w r eeds that are 

 not wholly submerged. Hydrocampa, removed from 



