170 Illinois State Laboratory of Natural History. 



matter containing numerous diatoms, and of small cells, isolated 

 and in chaplets, o£ what Prof. Burrill thinks is a Conferva, — 

 one of the algae which grow on moist surfaces. 



ORDER TRICHOPTERA. (Case Flies.) 



Larvae of this group usually construct movable or fixed 

 cases with openings at the ends. These cases are sometimes of 

 peculiar shape, and oftener attract attention than the winged 

 insects. They may be cylindrical, cone-shaped, spiral, like a 

 flattened ink bottle, etc., and generally have bits of vegetation, 

 or sand, fastened over the outer surface. The adults are small 

 obscurely-colored insects, which usually take no food, and after 

 depositing their eggs soon die. The eggs, enclosed in a gela- 

 tinous material, are placed on aquatic plants, the females, it is 

 thought, sometimes descending into the water for this purpose. 

 The larvae feed on vegetable matter, such as dead leaves, stems, 

 and wood, but sometimes devour also small insects and crusta- 

 ceans. Those I have examined are abundant in small streams in 

 central Illinois, and make large cj^lindrical cases, to the outside 

 of which are fastened, longitudinally, numerous small sticks. 

 The alimentary canal of this larva has always been found filled 

 with decayed woody vegetable matter. The pupa3 are formed 

 in the cases, which are, if movable, fastened down by the larva 

 previous to pupation. 



Trichoptera, larva (1). 



The common case-fly larva at Quincy was a somewhat un- 

 usual one as to habits. Most of our species creep slowly about 

 on vegetation or on the bottom. This one is a free-swimming 

 larva, and one or two were always taken when the surface net 

 was drawn over the deepest water of Quincy Bay. It was cap- 

 tured on one occasion in the swift current of the river in a net 

 drawn after the steamer " Hannibal Eagle." The case is 

 trumpet-shaped, gradually decreasing in caliber from the larger 

 end (which has a diameter of about .07 inch) to the smaller 

 extremity, where the diameter is about .03 inch. The outside 

 of the case has scattered bits of dead vegetable matter fastened 

 over it, and numerous minute particles of sand. Fastened to 



