August, 1944 



Ross: Caddis Flies of Illinois 



101 



Illinois Records. — Des Plaines, Fox 

 River: May 26, 1936, H. H. Ross, 2 larvae. 

 Kankakee, Kankakee River: May 17, 

 1935, H. H. Ross, 2 pupae; Aug. 8, 1935, 

 Ross & DeLong, 1 larva. Momence: May 

 17, 1931, Ross & Burks, 1 S ; June 4, 1932, 

 Prison & Mohr, 4 <5 ; Aug. 1, 1935, Ross 

 & Burks, 1 S ; Mav 26, 1936, H. H. Ross, 

 1 S ; July 14, 1936, B. D. Burks, U , 2 

 larvae; Aug. 3, 1936, C. O. Mohr, I S ; 

 Aug. 4, 1936, Frison & Burks, S S ; May 

 17, 1937, Ross & Burks, $ S, \ S pupa; 

 Sept. 7, 1937, Frison & Ross, 1 $ ; May 5, 

 1938, Ross & Burks, 3S. St. Charles: 

 June 18, 1931, T. H. Frison, \S. Spring 

 Grove: May 14, 1936, Ross & Mohr, 3$, 

 19,2 pupae, 8 larvae; June 12, 1936, Ross 

 & Burks, 5 5,12,1 $ pupa; Nippersink 

 Creek, May 19, 1938, Ross & Burks, 2$. 

 Wilmington, Kankakee River: April 23, 

 1930, Ross & Mohr, 1 pupa; April 10, 1935, 

 Ross & Mohr, many larvae; April 23, 1935, 

 Ross & Mohr, 7 pupae, many larvae; May, 

 1935, reared in cage, Ross & Mohr, many 

 pupae; May 12, 1935, Frison & Ross, $ S , 

 9 9 ; May 17, 1935, H. H. Ross, S $, 

 9 9 ; May 27, 1935, Ross & Mohr, S $ , 

 9 9 , many pupae and larvae; June 6, 1935, 

 Ross & Mohr, S $,79, many larvae ; May 

 17, 1937, Ross & Burks, S S, 9 9. Wil- 

 mington: Aug. 3, 1937, at light, Ross & 

 Burks, 1 $ . 



Scalaris Group 

 Hydropsyche aerata Ross 



Hydropsyche aerata Ross fl938rt, p. 144); 



Larva. — Fig. 349. Length 13 mm. Head, 

 thoracic sclerites and legs yellow, dorsum 

 of the head with a somewhat cross-shaped 

 dark brown mark, pronotum minutely speck- 

 led with brown. Frons almost flat, anterior 

 margin straight. Head and pronotum with 

 only a few scattered long hairs, in general 

 appearing polished. 



Adults. — The two sexes are very dissim- 

 ilar in general appearance. Male, fig. 392: 

 length 9 mm.; head and body dark brown, 

 antennae and legs white ; wings white with 

 definite brown markings forming a distinc- 

 tive pattern; eyes very large, twice as wide 

 as the antero-dorsal distance between them; 

 genitalia, fig. 372, with tenth tergite up- 

 turned and deeply incised; apex of aedeagus 



with an open area between lateral processes. 

 Female: length 10 mm.; color dark brown, 

 the wings mottled with various shades of 

 brown and resembling other females of the 

 genus, similar to fig. 393; genitalia as in 

 fig. 386G. 



Myriads of this uniquely marked species 

 have been taken at Illinois localities along 

 the Kankakee River, in the rapids of which 

 the larvae and pupae have been found. 

 Other than in this area, we have taken only 

 one or two records from the eastern part of 

 the state. The adults emerge from May 

 through most of August. 



The present known range of the species 

 is very small, fig. 15, and includes Illinois, 

 Indiana and southern Michigan. All the 

 records indicate a preference for medium- 

 sized to large, rapid rivers. 



Illinois Records. — Aurora: July 17, 

 1927, at light, Frison & Glasgow, 1 $ . 

 Kankakee, Kankakee River: Aug. 1, 1933, 

 Ross & Mohr, 1 $ ; May 26, 1935, Ross & 



Fig. 392. — Hydropsyche aerata, cf . 



