34 



Illinois Natural History Survey Bulletin 



Vol. 23, Art. 1 



moderately incised, fig. 126, or not 

 incised at all, fig. 124 3 



3. Ninth tergite produced into a long, 



narrow, forked process which ex- 

 tends over tenth tergite, fig. 122. . . 



vibox, p. 36 



Ninth tergite not produced into a 

 forked process, fig. 123 4 



4. Tenth tergite heart shaped and point- 



ed at apex, fig. 123, long and shallow; 

 aedeagus with a U-shaped process 

 at the end of the lateral arms of the 



aedeagus glaberrima, p. 35 



Tenth tergite short and deep, divided 

 down meson, not forming a round, 

 dorsal plate; aedeagus without U- 



shaped processes at the end of the 

 lateral arms, figs. 124, 126 5 



5. First segment of claspers with ventral 



margin almost straight from base to 

 apex; aedeagus without a ventral 



plate, fig. 124 fuscula, p. 36 



First segment of claspers with ventral 

 margin humped to form a definite 

 shoulder near base; aedeagus with 

 large, scoop-shaped ventral plate 

 below central portion, fig. 126 6 



6. Apical segment of clasper incised to 



form a definite dorsal heel, figs. 126, 



127 7 



Apical segment of clasper not incised, 

 only sinuate, fig. 125, so that the 



FUSCULA 



I32E 



Figs. 128-132. — Rhyacophila, female genitalia. J and B, apex of abdomen, ventral and 

 lateral aspect; C, tenth tergite; D, eighth sternite; E, eighth segment, lateral aspect. 



