August, 1944 



Ross: Caddis Flies of Illinois 



a hymenopterous parasite, Hemiteles b'tan- 

 nulatus Gravenhorst, from cases of Limne- 

 philus indivisus from Itasca Park, Minne- 



sota. In Europe the hymenopterous para- 

 site Agriotypus has been reared from caddis 

 fly larvae. 



HABITAT PREFERENCE 



Over most of Illinois, caddis fly habitats 

 are streams and rivers with medium to slow 

 current, with fairly warm water and fre- 

 quently with a heavy silt deposit. This 

 statement applies not only to the main water 

 arteries but also to most of the small creeks 

 and branches which feed them. These 

 streams run through the highly developed 

 agricultural area which includes most of 

 the state. Markedly different types of 

 streams are either restricted to small areas 

 such as the Ozark Hills, or very locally 

 distributed, as for example, the spring-fed 

 brooks at Elgin. 



In Illinois, natural lakes are restricted 

 to the northeastern corner of the state and 

 are all of glacial origin. Here are found a 

 few typical lake species but they do not 

 form a large proportion of our caddis fly 

 fauna. Artificial lakes are common over 

 most of the state but have few caddis flies. 



Typical Large Rivers 



The Mississippi, Illinois and Wabash are 

 in some respects typical not only of our 

 large rivers but also of the more sluggish 



lower portions of smaller ones such as the 

 Fox and Kaskaskia. These have enormous 

 numbers of the net-spinning caddis flies, 

 especially Potamyia flava, Cheumatopsyche 

 campyla and Hydropsyche orris, b'tdens and 

 simulans. The case-making species are con- 

 fined almost entirely to the Leptoceridae, 

 and those taken in abundance include Oece- 

 tis inconspicua and avara, Athripsodes can- 

 cellatus and transversus, and Leptocella Can- 

 dida, exquisita and diarina. Abundant web- 

 spinning forms include Neureclipsis crepus- 

 cularis and Cyrnellus niarginalis. 



In these situations there are generally 

 few or no very early season species. Most 

 of the species occur in the adult stage 

 throughout the late spring and summer 

 months with continuous generations. 



Unusual Large Rivers 



Kankakee River. — Of all the rivers in 

 Illinois, the Kankakee, fig. 5, is the most 

 unusual from the standpoint of the caddis 

 fly fauna. Here we have taken 12 species 

 found nowhere else in the state. Several 

 other species are common here but rarities 



SS' 



Fig. 5. — Kankakee River at Wilmington, Illinois. This is one of three rapids on the lower 

 portion of this river, in all of which caddis flies of unusual interest are found. 



