August, 1944 



Ross: Caddis Flies of Illinois 



63 



MACULATUS /' PENTUS ^ CINEREUS 



Figs. 249-261. — Polycentropus, female genitalia, ventral aspect. 



shorter, without expanded apex and 

 with toot not angulate, fig. 252. . . . 

 glacialis, p. 68 



21. Bursa copulatrix with a wide base and 



long, vasiform, sclerotized apical 

 structures; internal structure of 

 ninth segment as in fig. 253, with 

 rounded, nearly approximate apical 

 lobes which are sclerotized only at 



apex centralis, p. 64 



Bursa copulatrix shaped differently, 

 figs. 254-259; internal structure 

 with longer lobes which are farther 

 apart 22 



22. Ninth sternite with ovoid sclerotized 



lobes on each side of bursa; eighth 

 sternite nearly triangular with the 



sides slightly sinuate, fig. 254 



species a, p. 66 



Ninth sternite without ovoid lobes as 

 in fig. 254; eighth sternite with apex 

 more rounded, often nearly truncate, 

 figs. 255-259 23 



23. Ninth sternite without sclerotized 



bands; bursa supports sometimes 

 heavily sclerotized, figs. 255-257.. 

 Ninth sternite with sclerotized bands 

 in addition to supports of bursa 

 copulatrix, figs. 258, 259 26 



24. Upper portion of bursa supports thick, 



wide and twisted, fig. 255, and lower 

 portion forming a thick bridge below 



bursa pixi, p. 66 



Bursa supports much more slender, 



24 



