August, 1944 



Ross: Caddis Flies of Illinois 



87 



Dorsum of abdomen with wide, short, 

 scalelike hairs mixed with plain 

 hairs, fig. 342, these scales some- 

 times sparse but usually conspicu- 

 ous on the sixth, seventh or eighth 

 tergites 



Dorsum of abdomen with only narrow, 

 long, scalelike hairs mixed with plain 

 hairs, fig. 344 



10 



342 A 



342 



mmmm 



343 



345 



Fig. 342. — Hydropsyche simulans larva, apex 

 of abdomen, dorsal aspect; A, enlarged portion 

 of epidermis. 



Fig. 343. — H. arinale larva. 



Fig. 344. — H. recurvata larva. 



Fig. 345. — H. aerata larva, apex of abdo- 

 men, ventral aspect. 



5. Head chiefly yellow or straw color 



with a dorsal mark resembling a 

 cross, fig. 349, the surface shining 

 and without short, black hair; base 

 of anal legs with a patch of brown, 



flat spines, fig. 345 aerata, p. 101 



Head either with more extensive dark 

 markings, fig. 354, or with abundant, 

 short, black hair, or base of anal 

 legs without a patch of spines 6 



6. Entire dorsum and lateral portion of 



head bright brownish red, uniform 

 except for a fine pattern of yellow- 



ish spots, fig. 350; preclypeus with 

 sclerotized areas at sides, labrum 

 with yellow or pale hair. . .cuanis, p. 100 

 Dorsum of head with either a definite 

 pale and yellow pattern, fig. 353, or 

 mostly dark brown; preclypeus 

 without lateral sclerotized areas, la- 

 brum usually with pale hair 7 



7. Scale-hairs sparse on dorsum of ab- 



domen, on sixth segment no more 



abundant than in fig. 343 



arinale, p. 104 



Scale-hairs at least as abundant as in 

 fig. 342 8 



8. Head with dorsal pattern merging 



gradually and not contrasting much 



with ground color, fig. 352 



simulans, p. 104 



Head with a well-delimited dorsal, 

 dark brown mark contrasting with 

 ground color, figs. 353, 354 9 



9. Dorsal mark on head wider, extending 



full width of head, ending in line 

 with eyes, cut ofl^ with a sharper and 

 straighter margin, fig. 353; simple 

 hairs on abdomen as dark and con- 

 spicuous as scale-hairs. . .hageni, p. 103 

 Dorsal mark of head not extending to 

 margin of head, margin irregular, 

 fig. 354; simple hairs on abdomen 



much lighter than scale-hairs 



frisoni, p. 105 



10. Head mostly black or blackish brown 

 with one or two mesal yellow 



squares, fig. 355 slossonae, p. 99 



Head with a definite checkered pat- 

 tern, the checks either surrounded 

 by black, fig. 356, or indicated by 

 dark bars on a yellow ground, fig. 



357 bifida, p. 97; bronta, p. 



98; cheilonis, p. 98; recurvata, p. 99 



Adults 



1. Genitalia with a prominent aedeagus, 



fig. 358 (males) 2 



Genitalia without an aedeagus, fig. 

 390 (females) 28 



2. Aedeagus with a pair of ovoid, dorsal 



sclerites near apex, figs. 358-367. . 3 

 Aedeagus without a pair of ovoid, dor- 

 sal sclerites near apex, figs. 368- 

 383 13 



3. .^pex of aedeagus with a lateral pair of 



membranous arms directed basad, 



fig. 358 4 



Apex of aedeagus with lateral pro- 

 cesses sessile or lacking, fig. 361 .... 6 



4. Aedeagus just basad of dorsal sclerites 



bearing a dorsal pair of large, stout 

 hooks curved laterad, fig. 358. . . . 

 walkeri, p. 96 



