172 Illinois State Laboratory of Natural History. 



easily disposed and retained on the hook. They are furnished 

 with seven or eight pairs of respiratory filaments along the 

 sides of the body for use in the water, and have, besides, 

 breathing pores (spiracles), which they use when they leave 

 the water to pupate in the earth. The tarsi have two claws. 

 The eggs are deposited in large, whitish discoidal masses on the 

 leaves of trees and on the sides of boats aud barges. 



Corydalis cornutus, Linn. (Hellgramrcite.) 



(Walsh and Riley, Am. Ent., i, 61, 1868.) 

 The larvae and adult of this large insect often attract the 

 attention of those who live on our rivers. The species is not 

 often seen in the interior of the State. Along the Mississippi 

 River it is very common, though its abundance is not commonly 

 apparent excepting during the egg-laying season. In August 

 the wood barges and boats in the bay were resorted to by the 

 females, and the masses of eggs were left in numbers upon the 

 timbers. 



ORDER HEMIPTERA. (True Bugs.) 



This is one of the most important groups of aquatic 

 insects, both oq account of the food its members furnish to 

 fishes, and also because of the serious injuries which some bugs 

 do to fish eggs and fry. The genera Ranatra and Beh)stoma 

 are especially to be remembered as containing some of che worst 

 insect enemies to fishes of which we know. Most of ttiem 

 begin a predatory life as soon as hatched from the eg^, and 

 continue it without cessation throughout their existence. The 

 common food consists of larvie of other insects, mollusks, and 

 the like. The eggs are generally deposited on aquatic plants, 

 sometimes enclosed in gelatinous matter, but in many cases 

 quite naked. Corisa sometimes places its eggs on the shells of 

 crayfishes. Eight families of the order have common repre- 

 sentatives inthe waters of the State. Of these, five appear in 

 the collection made at Quincy. 



Family HYDROBAXiDiE. (Crazy Bugs.) 



Limnotrechiis mavjinatus, Say. 



{Gerris marginatus^ Say, Heteropterous Hemiptera, 1831, 



807.) 



