August, 1944 



Ross: Caddis Flies of Illinois 



237 



ment with 4-6 rows of micro-hooks, 



fig. 813 avara, p. 240 



Dorsal hump ot first abdominal seg- 

 ment without micro-hooks 3 



3. First abdominal sternite with a row of 



hairs extending across the segment 4 

 First abdominal sternite with only one 

 , or two pairs of setae 6 



4. Meso- and metanotum each with a 



lateral tuft of 10-20 hairs; first ab- 

 dominal sternite with a row of about 

 50 hairs; ninth tergite with about 



25 hairs; head spots very dark 



ochracea, p. 244 



Meso- and metanotum without dis- 

 tinct lateral tufts; first abdominal 

 sternite with a row of only 25 hairs; 

 ninth tergite with only 8-10 hairs; 

 head spots various 5 



5. Head with three dark areas on and 



near frons, fig. 812 species a, p. 244 



Head without such dark areas, fig. 834 

 inconspicua, p. 242 



6. Left mandible with ventral aspect 



slightly convex but without creases, 



fig. 814 eddlestoni, p. 240 



\'entral aspect ot left mandible with a 

 deep crease running from apical 

 tooth, fig. 815 species b, p. 244 



Adults 



1. Apex of abdomen with movable clasp- 



ers, figs. 816-824 (males) 2 



Apex of abdomen without claspers, 

 figs. 825-832 (females) 10 



2. Tenth tergite consisting of a pair of 



long, slender, cylindrical, sclero- 

 tized rods, each bearing two stout, 



peglike setae, fig. 816 3 



Tenth tergite either very short, com- 

 posed of a single process, fig. 824, 

 or with rods bladelike and without 

 pegs, fig. 819 4 



3. Claspers produced into a long, apical 



finger, fig. 816 scala, p. 241 



Claspers in general truncate at apex, 

 fig. 817 eddlestoni, p. 240 



4. Claspers somewhat kidney shaped, 



much higher than long, fig. 818. . . . 



avara, p. 240 



Claspers elongate, longer than high. . 5 



5. Tenth tergite formed of a pair of 



bladelike structures wide at base and 

 tapering to a downcurved, narrow 

 apex; claspers with basal portion 

 wide and apex with a very short 



projection, fig. 819 osteni, p. 241 



Tenth tergite formed ot either a single 

 mesal projection, fig. 821, or very 

 short, fig. 820 6 



6. Claspers with mesal margin incised to 



form a short mesal tooth, fig. 820. . 



ochracea, p. 244 



Claspers with mesal margin straight 

 or sinuate, not incised, figs. 821- 

 824 7 



7. Abdomen with sixth and seventh or 



seventh and eighth tergites finely 

 and distinctly reticulate; apical 

 finger of claspers long and converg- 

 ing at apex, fig. 822 8 



.'\bdomen with none of tergites recticu- 

 late; apical finger of claspers diverg- 

 ing, fig. 824 9 



8. Tenth tergite twice as long as cerci, 



fig. 821; seventh and eighth tergites 



reticulate persimilis, p. 243 



Tenth tergite about as long as cerci, 

 fig. 822; sixth and seventh tergites 

 reticulate cinerascens, p. 241 



9. Upper margin of claspers evenly sin- 



uate, aedeagus elongate and with the 

 apical beak projecting straight, fig. 



823 immobilis, p. 241 



Upper margin of claspers deeply 

 emarginate to form a prominent 

 baso-dorsal lobe, aedeagus almost 

 circular, the beak directed ventrad, 

 fig. 824 inconspicua, p. 242 



10. Bursa copulatrix attached to a large, 



many-lobed, heavily sclerotized in- 

 ternal structure with a pair of long, 

 anteriorly directed, sclerotized rods, 



fig. 825 persimilis, p. 243 



Bursa copulatrix not attached to a 

 sclerotized, lobed internal structure, 

 fig. 826 11 



11. Eighth sternite with a purse-shaped, 



sclerotized area, fig. 826. . . osteni, p. 241 

 Eighth sternite without such an area, 

 at most with sclerotized lines, fig. 

 827 12 



12. Ninth sternite produced into a pair of 



short "ears" on each side of lobes 

 of tenth segment, fig. 827; subgenital 

 plate outlined by a more or less cir- 

 cular black line 13 



Ninth sternite not produced into 

 "ears"; subgenital plate outlined as 

 a diamond-shaped or vasiform area, 

 figs. 830-832 15 



13. Subgenital plate angled outward across 



middle, the base membranous, the 

 apical declivity with a pair of scle- 

 rotized plates together forming a 

 shallow, concave basin, fig. 827. . . . 



cinerascens, p. 241 



Subgenital plate with sclerotized plates 

 weaker and occupying basal instead 

 of apical portion, fig. 828 14 



14. Bursa copulatrix as in fig. 828, with 



apex nearly truncate and basal por- 



