August, 1944 



Ross: Caddis Flies of Illinois 



the streams, and they are muddied only 

 temporarily after rain. The banks are 

 wooded with dense stands of trees which 

 form a canopy over the water when the 

 leaves are out. In early spring, beginning 

 in March, these streams abound in a variety 

 of caddis flies; case makers crawl over the 

 rocks, and others crawl in the moss or under 

 the stones. 



The taxonomic composition of all these 

 Ozark streams is virtually the same and 

 it is remarkably distinct from all other 

 streams in the state. Species confined to 

 this area include Rhyacophila fenestra, Ag- 

 apetus mini, Dolophiliis shawnee and a num- 

 ber of Hydroptilidae, among them Ochro- 

 trichia shawnee, eliaga, anisca and unio, 

 Hydroptila -virgata, vala and amoena and 

 Neotricliia riegeli and collata. Species of 

 Hydropsyche, Cheumatopsyche and other 

 genera which are common in other streams 

 of the state are a rarity here. 



Of unusual interest in this area are four 

 other caddis flies. Chimarra feria is very 

 common in these streams but has been taken 

 nowhere else in the state ; C. obscura, which 

 we find in several other parts of Illinois, 

 has not been taken in our recent collecting 

 in the Ozark Hills but was apparently fairly 

 common in them around 1900, judging by 

 collections made at that time by C. A. Hart. 

 Taken at the same time and place by Hart 

 were several collections of a species of 

 Athripsodes believed to be flavus (see p. 

 228) ; this species has not been taken in the 

 area in our recent survey. The fourth 

 species is Neophylax autumnus. These lim- 

 nephilid larvae make a hard stone case and 

 are exceedingly common in most of the 

 Ozarkian streams. They occur sparingly in 

 other parts of the state. 



Early in summer these streams tend to 

 dry up, often going beyond even a pool stage 

 to the point at which no water can be seen 

 along the entire course of the stream. This 

 dry period frequently extends into Novem- 

 ber and December before water again flows; 

 yet by spring the life in the water is invari- 

 ably present in great abundance. The man- 

 ner in which many of the caddis flies survive 

 through this dry period is unknown. Exam- 

 ination of the dry bed has given information 

 on three species which pass through this 

 period in the larval or pupal stage; it is 

 likely that some of the others pass it in the 

 egg stage. 



Where the stream bed is shaded and the 



ground contour provides some subsurface 

 drainage into it, stones and shelflike out- 

 crops may remain damp underneath indefi- 

 nitely. In these damp situations we found 

 large numbers of Neophylax autumnus lar- 

 vae aestivating; later in the autumn while 

 the stream was still dry these larvae trans- 

 formed to pupae, and we watched actual 

 emergence of adults from these nearly dry 

 cases. Digging a few inches into the stream 

 bed, we discovered active larvae of Chimar- 

 ra feria and a healthy pupa of Rhyacophila 

 glaberrima under stones at a level where 

 stones and sand were moist. In no case did 

 we find signs of active forms along portions 

 of the stream bed which were not shaded. 



Unusual Small Streams 



Scattered around the state are a number 

 of streams quite different in character and 

 fauna from the usual stream running 

 through most of the agricultural land. Ex- 



Fig. 6. — Brook in Botanical Gardens at 

 Elgin, Illinois. This and three parallel sister 

 brooks are fed by seepage and are cold and 

 clear throughout the year. Here live several 

 northern caddis flies found nowhere else in the 

 state. 



