21 8 Aquatic Organisms 



Caddis -fly pupae 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 Triaenodes. 



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 Hydropsyches, 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 weeds that are 

 not wholly submerged. Hydrocampa, removed from 



