August, 1944 



Ross: Caddis Flies of Illinois 



227 



18. Base of claspers with ventral margin 



produced into a lobe, fig. 790 



transversus, p. 233 



Base of claspers with ventral margin 

 rounded, fig. 791. . . cancellatus, p. 233 



19. Ninth sternite with a pair of finger- 



like, apico-mesal lobes, fig. 792. ... 20 

 Ninth sternite without digitate lobes, 

 at most with short points, fig. 794 21 



20. Bursa copulatrix with lateral bands 



curved ventrad and convoluted near 

 attachment; only a small, triangular 

 sclerite between bursa and dorsal 

 apodeme of tenth tergite, fig. 792 



tarsi-punctatus, p. 229 



Bursa copulatrix with lateral bands 

 flat to attachment; a large sclerite 

 almost filling space between bursa 

 and dorsal apodeme of tenth tergite, 

 fig. 793 alagmus, p. 229 



21. Ninth sternite with plates deeply con- 



cave, apico-mesal corners pointed, 

 lateral margin upturned and angu- 



late near base, fig. 794 22 



Ninth sternite not concave, not with 

 lateral margin upturned or angu- 

 late, figs. 796-807 23 



22. Sclerotized halves of ninth sternite 



sharply tapered to base, lateral 

 margin sharply angulate; bursa 

 copulatrix with sides appressed to 



body, fig. 794 flavus, p. 228 



Sclerotized halves of ninth sternite 

 almost truncate at base, lateral mar- 

 gin only rounded at projection; 

 bursa copulatrix with sides flaring 

 laterad, fig. 795 ancylus, p. 227 



23. Tenth segment with lateral plates as 



long as ninth sternite, fig. 796 



dilutus, p. 231 



Tenth segment with lateral plates 

 much shorter than ninth sternite, 

 fig. 797 24 



24. Ninth sternite with lateral margins 



angling more mesad than caudad 

 from base, the angled portion 

 marked by an internal shelf, fig. 797 25 

 Ninth sternite with lateral margins 

 not angling so sharply, either the 

 internal shelf absent or not angling 

 mesad more than in fig. 805 26 



25. .Apical portion of ninth sternite wide, 



fig. 797 transversus, p. 233 



Apical portion of ninth sternite nar- 

 rower, fig. 798 cancellatus, p. 233 



26. Bursa copulatrix situated on sclero- 



tized ribbons which extend far past 

 the bursa to the seventh segment, 



fig. 799 annulicornis, p. 232 



Attachment ribbons of bursa copula- 

 trix not extending anterior of bursa 27 



27. Bursa copulatrix with wide lateral ex- 



pansions, fig. 800 28 



Bursa copulatrix with lateral expan- 

 sions absent or small, fig. 806 29 



28. Attachment of bursa copulatrix chiefly 



membranous with a single pair of 

 flat sclerites just above bursa, fig. 



800 resurgens, p. 230 



Attachment of bursa copulatrix con- 

 sisting chiefly of a sclerotized ribbon, 

 fig. 801 angustus, p. 231 



29. Ninth sternite with large lateral plates 



and a narrow, mesal tongue, all 

 heavily sclerotized, as in fig. 802. , . 



punctatus, p. 234 



Ninth sternite with mesal area indis- 

 tinct or much wider, fig. 807 30 



30. Bursa copulatrix triangular, fig. 803 



submacula, p. 235 



Bursa copulatrix U-shaped, figs. 804- 

 807 31 



31. Bursa copulatrix attached at the end 



of a long, vasitorm, sclerotized struc- 

 ture, fig. 804 eruUus, p. 235 



Bursa copulatrix attached to short 

 membranous folds or to paired scle- 

 rotized ribbons 32 



32. Bursa copulatrix oval, without latero- 



ventral points, fig. 805 



mentieus, p. 232 



Bursa copulatrix U-shaped or some- 

 what vasiform, with sharp latero- 

 ventral points, figs. 806, 807 2)i 



33. Points near top of bursa copulatrix; 



ninth sternite composed chiefly of a 

 single, large sclerotized plate arcuate 



across apex, fig. 806 saccus, p. 234 



Points near middle of bursa; ninth 

 sternite composed of a pair of large, 

 lateral sclerotized plates and a 

 smaller, nearly square mesal plate, 

 fig. 807 erraticus, p. 235 



Athripsodes ancylus (\ orhies) 



Leptoceriis ancylus V'orhies (1909, p. 691); 



d', 9. 



Larva. — Fig. 766. Length 8 mm. Head 

 very dark brown with pale area around eyes 

 and subfrons, forming a pale U with a few 

 dark dots in upper portion; pronotum dark 

 brown with a lateral white spot; legs light 

 brown. The frontal areas more than half 

 width of Irons. Pronotum with only long 

 scattered hairs on anterior margin. Meso- 

 notum with a lateral tuft of about 10 hairs, 

 central area with only three or four scat- 

 tered pairs of hairs, sclerotized bars thin 

 and not at all sharply angled. 



