August, 1944 



Ross: Caddis Flies of Illinois 



77 



treat under and about trash, logs, stones 

 and any other haven. In front of this retreat 

 they build a net which is reputed to strain 

 food from the flowing water, fig. 4. For 



Fig. 281. — Hydropsyche simulans, larva. 



pupation they spin an ovoid cocoon near the 

 retreat, generally using sand, stones and bits 

 of trash. 



Characters of both mature and immature 

 stages show no real benefit to be derived by 

 dividing this family in subfamilies. Because 

 it simplifies the keys to treat the entire 

 family as a unit with no established group- 

 ings and combinations of genera to follow, 

 subfamily treatment has been disregarded. 



KEY TO GENERA 

 Larvae 



1. Head with a broad, flat dorsal area 



set off" by an extensive arcuate ca- 

 rina, fig. 415. . . Macronemum, p. 114 

 Head without a dorsal area set off by a 

 carina, fig. 304 2 



2. Left mandible with a high thumblike, 



dorso-lateral projection, fig. 282. . . 



Genus A, p. 83 



Left mandible without a dorso-lateral 

 projection, at most with a carina, 

 fig. 283 3 



3. Stridulator of front leg forked, fig. 291 4 

 Stridulator of front leg not forked, fig. 



292 5 



4. Prosternal plate with a pair of poste- 



rior sclerites, fig. 293. Basal tooth 



of mandibles single, fig. 284 



Hydropsyche, p. 86 



Prosternal plate without a pair of 

 sclerites posterior to it, fig. 294. 

 Basal tooth of mandibles double. 



fig. 285 Cheumatopsyche, p. 108 



5. Quia rectangular and long, separating 

 genae completely, fig. 296; each 

 branched gill with all its branches 

 arising at top of basal stalk, fig. 



298 6 



Gula triangular and short, genae there- 

 fore fused for most of their length, 



283 



284 



287 



288 



289 290 



Hydropsychidae Larvae, Mandibles 



Fig. 282. — Hydropsychid Genus A. 

 Fig. 283. — Potamyia flava. 

 Fig. 284. — Hydropsyche cheilonis. 

 Fig. 285, — Cheumatopsyche campyla. 

 Fig. 286. — Diplectrona modesta. 

 Fig. 287. — Smicridea fasciatella. 

 Fig. 288. — Macronemum zebratum. 

 Fig. 289. — Parapsyche cardis. 

 Fig. 290. — Arctopsyche grandis. 



