900 



FRESH-WATER BIOLOGY 



THE CADDISFLIES (Order Trichoptera) 



The caddisflies constitute a large group of insects, nearly all of 

 which are aquatic in their immature stages. Among the adults 

 are many pretty species of soft colors and great elegance of form. 

 Having rudimentary mouth parts they are short-lived. They are 

 chiefly nocturnal in habits and fly to lights, often in great num- 

 bers. Some are diurnal and hover over water in long sustained 

 horizontal flight; others dance up and down in companies under 

 the shelter of streamside trees. No insects are more common 

 about the wharf lights on the shores of our great lakes. 



The larvae exhibit great diversity of structure and habits. Much 

 excellent work has been done on them in Europe, but our American 

 forms are little known. The most familiar larvae are the well 

 known " caddisworms " that construct portable cases (Fig. 1371), 



>v 



FIG. 1371. Caddisworm cases. (Drawn by Mrs. J. H. Comstock.) 



in which to live, and carry them about on their backs. These 

 cases are made out of a great variety of materials: sticks, small 

 stones, sand grains, bits of shell, of leaves or of bark; in short, almost 

 any solid material suitably small and available. In many species 

 the construction of the cases is so uniform in pattern and materials 

 that the larvae may be known by the houses which they drag 

 about. The larvae of the-Phrygeaneidae construct cylindrical cases 

 made of bits of stems, grass, etc., placed lengthwise in a continu- 



