156 lUinois State Laboratory of Natural History. 



spring-fed streams in Illinois, but the flies are not known to 

 damage stock in this region (central Illinois). The larva? of 

 this family are eaten by trout, and occur in the stomachs of 

 other smaller fishes. The pupa^ live in leathery cases attached 

 to the underside of stones and other objects in the water. The 

 adult fly emerges under water in the spring of the year. Cedar 

 Creek is exactly suited to these insects, and we should expect 

 to find them there at the proper season. 



The families Culicidse and Chironoraidae contain the mos- 

 quitoes and gnats. The larvaB occur in water at all times of 

 the year, so that in all probability a succession of broods are 

 reared each season. Some species, at least, are found in water 

 when cold weather comes in the fall, and doubtless remain in 

 the larval condition till the next season. The eggs are placed 

 in small masses on the surface of the water, where they float 

 till the larva? emerge. The food is believed, commonly, to be 

 decaying organic matter, so that the larva? have been thought 

 to ofEset in a measure, as fish-food and as scavengers, the inflic- 

 tions of the adults. They are extremely common, and may be 

 captured at night in surface nets literally by the pint. 



The family Tabanida? (the horse flies) contains a number 

 of species with aquatic larva\ The eggs, which are elongated, 

 smooth and shining, and of a dark color, are deposited in 

 masses by the flies on rushes and other aquatic plants in the 

 latter part of summer. The larvte live during the winter in 

 the water, lurking about under submerged wood or refuse. 

 They are carnivorous, and with their strong mouth parts can 

 inflict a severe bite. From their strength and activity they 

 must destroy great numbers of the smaller aquatic animals. 

 One kept by the late B. D. Walsh, fed upon a number of mol- 

 lusks, pushing its way into the shells as far as it could, as it 

 devoured the owners. Notwithstanding their aggressive ways, 

 quantities of them are sometimes taken by the channel catfish 

 (Ictalarus punctatus), and they are eaten, at least occasionally, 

 by bull pout. 



Family CuLiciDiE. (Gnats and Mosquitoes.) 

 Culex sp. 



The adults of one or more moscpiitoes were moderately 

 common about the sloughs. The larva' were not observed 



