10 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



flies unusual for Illinois but which differ 

 only slightly in general characteristics from 

 average streams in the vicinity. Prominent 

 among these is Quiver Creek, a fairly clear, 

 cold, rapid stream flowing through the 

 sand region just north of Havana, where 



cies. The larvae of these probably occur 

 on stones in the lake beyond the wading 

 line. 



Unique to our state fauna was a colony 

 of Hydropsyclie recurvata, found at the 

 south edge of Evanston. The larvae were 



Fig. 9. — Lake Michigan, at Zion, Illinois. Collecting within wading distance of shore 

 nets only scattered caddis fly records. Presumably more of the species live at a depth beyond 

 the grinding action of the undertow. Several species of Leptoceridae and Hydropsyche recur- 

 vata have been taken in Illinois only in or along Lake Michigan. 



we have taken a variety of interesting spe- 

 cies, the collection here including our only 

 record of Lype diver sa\ also the Salt Fork 

 and Middle Fork rivers, near Oakwood and 

 Danville, fairly large streams with many 

 riffles, rocky rapids and less silt than usual 

 in Illinois, streams in which rare species 

 such as HelicQpsyche borealis, Hydropsyche 

 frisoni and cheilonis, and many Hydroptili- 

 dae occur. 



Lake Michigan 



Our information concerning Lake Michi- 

 gan, fig. 9, is based chiefly on light collec- 

 tions along the shore. We have made shore 

 collections along the entire Illinois beach but 

 have been unable to take more than scat- 

 tered larvae in most places. 



Several species of the case-making genus 

 Athripsodes have been taken at lights along 

 the shore of the lake; these include dilutus, 

 erullus and resurgens, the last two consti- 

 tuting our only Illinois records of the spe- 



fairly common on the larger stones in 3 to 

 4 feet of water. This species is northern in 

 distribution and usually lives in rivers. Ap- 

 parently in this situation the wave action 

 and coldness of water were a sufKcient sub- 

 stitute for its usual conditions. 



Smaller Glacial Lakes 



In a few counties in the northeastern 

 corner of Illinois are a large number of 

 glacial lakes, fig. 10, similar in general 

 character to the northern lakes of Wiscon- 

 sin, Michigan and Minnesota. They vary 

 in depth, the shallower ones having extensive 

 marsh areas; their size varies from a few 

 to several hundred acres. The water is 

 clear, and the bottom is clean stones, a mass 

 of reed and sedge roots, or a bed of peaty 

 organic matter. Large beds of aquatic 

 plants abound in the little bays or the short, 

 sluggish connecting waterways; the predom- 

 inant plants are Elodea, Ceratophyllum, 

 Utricularia and Potamogeton. 



