August, 1944 



Ross: Caddis Flies of Illinois 



11 



These lakes have a caddis fly fauna quite 

 different from that of the river systems. 

 Conspicuous to a high degree are the Lep- 

 toceridae, whose cases may be found under 

 almost every stone and on every weed. The 

 Hydroptilidae, Molannidae and Psychomyi- 

 idae are the only other families represented 

 in numbers; the Limnephilidae and Phry- 

 ganeidae are almost entirely confined to 

 marsh situations. 



The commoner Leptoceridae include 

 Oecetis inconspicua, cinerascens, immobilis 

 and osteni, Triaenodes tarda and injusta, 

 Leptocella albida and exguisita, Leptocerus 

 americanus, Athripsodes dilutus and tarsi- 

 putictatus and JMystacides longicornis and 

 sepulchralis. Some of these, such as Oecetis 

 osteni, Mystacides longicornis and Lepto- 

 cella albida, are confined to lakes; most of 

 the others may be found in rivers, artificial 

 ponds or canals. The combination of all 

 these together, however, along with the 

 absence of Hydropsychidae and other stream 

 dwellers, is a phenomenon unique to these 

 lakes. 



The curious case of IMolanna uniopliila 



(see p. 206) occurs on sand bars in these 

 lakes; the minute cases of Orthotrichia and 

 Oxyethira abound on the stones and plant 

 stems; and the transparent, small, green 

 cases of Leptocerus americanus cluster in 

 the tips of the Ceratophyllum. 



Dead River Marsh 



At Zion, just north of Waukegan, there 

 is a large marsh area through the center 

 of which runs the Dead River, fig. 11, so 

 named because Lake Michigan, by backing 

 up into it, prevents its flow except at times 

 of heavy rain. This ribbon-like river is 

 therefore more like a marshy lake than a 

 stream ; its banks are crowded with exten- 

 sive beds of cyperaceous growth and its 

 channel is choked with mats of Ceratophyl- 

 lum and Polygonum. 



Living in this mass of plant stems is one 

 of the most extraordinary communities of 

 caddis flies in Illinois. Large, case-building 

 Phryganeidae are common, including Phry- 

 ganea cinerea and sayi, Banksiola selina, 

 Fabria inornata and Agrypnia vestita; the 



Fig. 10. — Grass Lake near Fox Lake, Illinois. Certain of the lake species, in particular the 

 Leptoceridae, are found in the lake proper rather than in the connecting channels. 



