August, 1944 



Ross: Caddis Flies of Illinois 



147 



21. Eighth sternite with a long, T- or Y- 



shaped area marked on middle, 



fig. 530 22 



Eighth sternite without central orna- 

 mentation, fig. 532 23 



22. Mesal sclerite of eighth sternite Y- 



shaped, without imbrications, fig. 



530 vala, p. 148 



Mesal sclerite of eighth sternite with 

 posterior margin truncate and the 

 wide portion imbricate, fig. 531. . . . 

 armata, p. 147 



23. Eighth sternite with apical 6 setae 



situated on individual stalks along 

 margin; tenth segment triangular, 



fig. 532 virgata, p. 148 



Eighth sternite with apical 6 setae 

 clustered on a mesal lobe as in fig. 

 531; tenth segment semicircular. . . 

 spatulata, p. 148 



24. Apex of eighth sternite produced into 



a long shield extending half the 

 length of the segment beyond meson 

 of tergite, fig. 533. .waubesiana, p. 150 

 Apex ot eighth sternite not produced 

 into a long shield 25 



25. Surface of eighth sternite bearing a 



single mesal plate near middle, fig. 



534 26 



Surface ot eighth sternite not bearing 

 a mesal plate, fig. 539 29 



26. Apex of eighth sternite incised on 



meson, fig. 534 perdita, p. 153 



Apex of eighth sternite produced on 

 meson, fig. 535 27 



27. Mesal plate of eighth sternite bell 



shaped, long and narrow, fig. 535. . 



ajax, p. 153 



Mesal plate of eighth sternite trapezoi- 

 dal, short and wide, figs. 536, 537. . 28 



28. Apex of eighth tergite with a narrow, 



straight-sided, straight-bottomed in- 

 cision without a mesal thickening, 



fig. 536 angusta, p. 152 



Apex of eighth tergite with incision 

 shallower, wider and with a mesal 

 thickening, fig. 537. .consimilis, p. 153 



29. Eighth segment with a large, spatulate, 



internal plate, best seen from ven- 

 tral aspect, fig. 538. . . grandiosa, p. 151 

 Eighth segment without a large in- 

 ternal plate, fig. 539 



albicornis, p. 1 5 1 



Hydroptila armata Ross 



Hydroptila armata Ross (1938^, p. 123); cf , 

 9. 



Larva (mature type). — Fig. 506. Length 

 about 5 mm. Head yellow with an inter- 



rupted posterior band; each thoracic notum 

 yellow with a central and a posterior dark 

 band. Body, fig. 541, similar in shape and 

 general appearance to that of Ochrotrichia 

 except for key characters. Each segment of 

 abdomen with a very small, inconspicuous 

 rectangular sclerite, difficult to detect. 



Case. — Shape as in fig. 465. Length about 

 5 mm. Purselike type, generally narrower 

 in cross section than Ochrotrichia, some- 

 times constructed of sand grains. 



Adults. — Length 2-4 mm. (generally 

 quite variable within this genus). Color 

 a mottled, salt-and-pepper combination of 

 white, gray, brown and dark brown. Sev- 

 enth sternite of male with a long, sinuate 

 process. Male genitalia, fig. 516: tenth ter- 

 gite wide at base, tapering toward apex, and 

 divided at extreme apex into a pair of sharp 

 lobes directed laterad; beneath the tenth 

 arise a pair of long processes which pro- 

 ceed beyond the apex of the tenth tergite 

 and then curve back above it; claspers long, 

 extreme tip sclerotized and upturned; aedea- 

 gus with small neck, long spiral process, and 

 long, slender apex which is armed at tip 

 with a short arm at right angles to stem. 

 Female genitalia, fig. 531: eighth segment 

 short, semimembranous, with a T-shaped, 

 ventral, imbricated area, and with an apical 

 lobe bearing six long setae. 



Association of males, females and larvae 

 was established by a collection of larvae and 

 mature pupae in Nippersink Creek at Spring 

 Grove, Illinois. In Illinois, as in other 

 states, the species has been taken only in 

 riffles of clear and moderately swift streams 

 of various sizes. The adults appear contin- 

 uously from May through September. They 

 are usually rare, but occasionally a fairly 

 large colony is found. 



The range of the species, including Illi- 

 nois, Indiana, Michigan, Oklahoma and 

 Wisconsin, seems to follow the western por- 

 tion of the oak-hickory forest. 



Illinois Records. — Fox Lake: July 15, 



1935, DeLong & Ross, 2$. Momence: 

 Aug. 21, 1936, Ross & Burks, 1 $ ; May 

 17, 1937, Ross & Burks, U , 6? (reared) ; 

 May 24, 1937, H. H. Ross, 1 $ ; June 22, 

 1938, Ross & Burks, $ $ . Oakwood, Salt 

 Fork River: Sept. 20, 1935, DeLong & Ross, 

 1^. Spring Grove: Nippersink Creek, 

 May 14, 1936, Ross & Mohr, 1 <5 , 3 ? 

 (reared), many larvae and pupae; June 12, 



1936, Ross & Burks, \i. Wilmington: 

 July 1, 1935, DeLong & Ross, 2$. 



