August, 1944 



Ross: Caddis Flies of Illinois 



97 



setae; from dorsal view the clasper groove 

 appears as a well-marked posterior swelling. 

 Allotype, female. — Niagara Falls, New 

 York: June 23, 1941, J. A. Ross. The 

 allotype is one of a mating pair. 



Hydropsyche vexa Ross 

 Hydropsyche vexa Ross (1938rt, p. 148); cf. 



This species is known only from the states 

 of Minnesota and Wisconsin. As with Hy- 

 dropsyche ivalkeri, it may ultimately be 

 taken in Illinois. The female genitalia are 

 illustrated by Denning (1943). 



Hydropsyche piatrix Ross 



Hydropsyche piatrix Ross (1938rt, p. 148); 



This species has been taken at the mouth 

 of large springs in Missouri and Arkansas, 

 but so far has not been taken in Illinois. 



Female. — Length 9 mm. Color and gen- 

 eral structure typical for group as described 

 for bifida below. Female genitalia, fig. 

 387//, with clasper groove more or less 

 indistinct, leading to the distinct clasper 

 receptacle invaginated under the dorsal cap 

 of the ninth tergite. The receptacle is 

 large, wide and fairly long, slightly swollen 

 dorsad and curving slightly posterad; its 

 ventral opening is wide. Lateral lobe of 

 ninth tergite of moderate length but nar- 

 row, with scattered setae. 



Allotype, female. — Greer Springs, Mis- 

 souri: June 7, 1937, H. H. Ross. This is 

 the type locality for the species. 



Hydropsyche bifida Banks 



Hydropsyche bifida Banks {\90Sb, p. 15); 

 cf , 9. 



Larva. — Fig. 356. Length 14 mm. 

 Ground color of head yellow with a dorsal 

 checkerboard pattern; thoracic sclerites light 

 brown, legs brownish yellow; abdomen gray 

 with brown hair. Frons slightly concave, 

 its interior margin straight. Hair of ab- 

 domen a combination of slender appressed 

 hair with a few erect, flattened but narrow- 

 hairs. 



Adults. — Length 8-10 mm. Head, tho- 

 rax and abdomen various shades of brown ; 

 legs straw color; antennae alternate bands 

 of straw color and brown; wings with a 



mottled irrorate pattern resulting in a salt- 

 and-pepper mixture which is slightly check- 

 ered. Male genitalia, fig. 367: apical proc- 

 esses of tenth tergite finger-like and round; 

 apical segment of clasper long and slender; 

 aedeagus with dorso-lateral processes tipped 

 with a small short spur; this spur may be 

 absent in some specimens. Female genitalia, 

 fig. 387, with the eighth tergite bearing an 

 apical comb, fig. 384/^, and with the lobes of 

 the sternite produced, slightly flared ventrad 

 and rather densely haired, fig. 388^ ; ninth 

 tergite as in fig. 387/. 



This is one of the very common species 

 of Hydropsyche in several streams in north- 

 ern Illinois, in particular the rapid portion 

 of the Rock River, Apple River and Nipper- 

 sink Creek. To date all our records of the 

 species are confined to the northern fourth 

 of the state. The adults begin emerging 

 early in May and continue through Septem- 

 ber. 



As is common with many other predom- 

 inantly northeastern species with a wide 

 seasonal emergence, bifida has a heavy flight 

 early in the season and a lesser one for the 

 remainder of the summer. 



The species has a wide range, appears to 

 be most abundant in the northcentral states, 

 and has not yet been taken east of central 

 New York. Records are available for the 

 following: Colorado, Illinois, Minnesota, 

 New York, Oklahoma, Ontario, Wisconsin 

 and Wyoming. 



Illinois Records. — Many males, females 

 and pupae, taken May 10 to August 23, 

 and many larvae, taken June 5 to June 12, 

 are from Amboy (Green River), Apple 

 River Canyon State Park, Dundee, Erie 

 (Rock Creek), Galena, Oregon, Rockford, 

 Rockton, Savanna, Spring Grove (Nipper- 

 sink Creek), Sycamore (tributary South 

 Kishwaukee River). 



Hydropsyche sparna Ross 



Hydropsyche sparna Ross (1938rt, p. 150); 



This distinctive species has not yet been 

 taken in the state. It has been captured 

 in extreme southwestern Michigan and can 

 be looked for in future collecting in Illinois. 

 It occurs abundantly to the north and east, 

 including Georgia, Michigan, Minnesota, 

 New York, North Carolina, Nova Scotia, 

 Ontario, South Carolina, Virginia and West 

 Virginia. 



