8 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



cept for those in the Ozark Hills, these 

 streams are isolated and local, probably 

 mere relics of habitat types which may have 

 been extensive and numerous before the 

 forests were cleared and the swamps drained 

 in advance of the plow. Some of the caddis 

 fly species occurring in these relic areas are 

 a rarity in this entire Central States area 

 but fairly common in streams of some of the 

 northeastern states. These individual locali- 

 ties have unusual species, many of them not 

 the same as those found in similar Illinois 

 localities. In Indiana and southern Michi- 

 gan this same type of relic area is found. 



Elgin. — Just north of the city of Elgin 

 are the unique Botanical Gardens situated 

 along the low, east bluff of the Fox River. 

 The park is an undisturbed remnant of the 

 original woods of the region and contains a 

 great variety of interesting herbs, shrubs 

 and trees. Out of the sides and base of the 

 bluff run many seepage rivulets which merge 

 to form five small brooks, each from 1 to 

 3 feet wide and a few inches deep, with a 

 stony bottom and a fairly rapid flow, fig. 6. 

 The water is cold and clear at all times. 

 In all of these streams the caddis flies are 

 extremely numerous, their cases literally 

 paving the bottom of the streams. Here 

 we have taken seven species found nowhere 

 else in the state: Glossosoma intermedium, 

 Dolophilus moestus, Rhyacophila vibox, 

 Hesperophylax designatus, Molanna try- 

 phena, Limnephilus rhombicus and Dru- 

 sinus uniformis. The first four are common, 

 especially the Glossosoma and Hesperophy- 

 lax, the cases of which may be found by the 

 thousands in these streams. 



Not only are these species peculiar to 

 these streams, but other species found in 

 neighboring streams are practically absent. 

 Other species which occur include chiefly 

 Lepidostoma liba and Diplectrona tnodesta, 

 both found only locally elsewhere in Illinois. 

 These conditions mark this Elgin group as 

 the most unusual and interesting of our 

 relic streams. 



Somewhat similar in nature are two other 

 spring-fed brooks near the Botanical Gar- 

 dens. In one we discovered a large colony 

 of Hydropsyche slossonae and in the other 

 a colony of Chimarra aterrima, both rare 

 and local in the state. 



Split Rock Brook at Utica. — This small 

 stream originates, fig. 7, in a spring near the 

 head of a short, wooded ravine and flows 

 along a channel 2 or 3 feet wide through 



a rich growth of herbs and shrubs. The 

 water is clear and cold and uniform in 

 volume except after hard rains. 



This stream has two distinct parts to its 

 course. In the upper, shaded portion we 

 have taken Diplectrona modesta, our only 

 Illinois record of Polycentropus pentus and 

 great numbers of the case maker N eophylax 



Fig. 7. — Brook at Split Rock, near Utica, 

 Illinois. Another spring-fed stream which is 

 clear and cold throughout the year. Unusual 

 species found here include Polycentropus pentus 

 and Ochrotrichia riesi and spinosa. (Photo by 

 Donald T. Ries.) 



autumnus. It was in this locality that we 

 found individuals of this last species emerg- 

 ing as adults in February and early spring, 

 the only such record for the entire genus 

 (see p. 203). 



In the lower portion, which flows through 

 a cleared area along the railroad right-of- 

 way, we found Ochrotrichia riesi and spin- 

 osa, to give us the only Illinois records of 

 these species. In this portion of the stream 

 the species mentioned in the preceding para- 

 graph were extremely scarce. 



Apple River Canyon State Park. — The 

 Apple River flows out of southern Wiscon- 

 sin and cuts across the extreme northwest- 

 ern corner of Illinois. Above and below 

 Apple River Canyon State Park the river 

 is sluggish, silty and nearly devoid of caddis 

 flies except for some of the tolerant species, 

 such as Oecetis inconspicua. Through the 

 park, however, it traverses a few miles of 

 rocky land, and has here a rock bottom, 

 faster current, shaded banks and practically 

 clear water, fig. 8. In this stretch we have 

 taken several species rare in the state, such 



