PLECOPTERA OF NORTH AMERICA 255 



anal process short, reaching to hind margin of 



eighth tergite, truncate behind fibula 



Knob on the seventh abdominal tergite trans- 

 verse, finely granulate and not extending much 

 over the hind margin of the seventh tergite; 

 supra-anal process long, slender, gradually ta- 

 pering to a point and extending to the knob on 

 the seventh tergite elongata 



7. Supra-anal process very long and slender (about 



as long as the first seven segments of the cerci) 

 and reaching normally to the middle of the sev- 

 enth abdominal tergite 8 



Supra-anal process generally not longer than the 

 first 4-5 segments of the cerci, reaching not 

 farther than the middle of the eighth abdomi- 

 nal tergite 9 



8. Small species (5 mm. in length) ; Sc does not 



reach the cord ; few or no costal crossveins ; R 



sinuate at origin of Rs gracilaria 



Large species (15 mm. in length) ; Sc reaches 

 about to the cord ; costal crossveins present ; R 

 not sinuate at origin of Rs grandis 



9. Eighth abdominal tergite with a small median 



raised tubercle; supra-anal process not longer 

 than the first three segments of the cerci— nana 

 Eighth abdominal tergite smooth, without a 

 raised process; supra-anal process longer than 

 the first three segments of the cerci 10 



10. Ninth abdominal tergite with two small raised 



tubercles, one each side of the median de- 

 pressed area ; Sc reaches almost to the cord ; R 

 of f orewing sinuate at origin of Rs ; supra-anal 

 process normally reaches to middle of eighth 



tergite; western species glabra 



Ninth abdominal tergite without any distinct 

 tubercles; Sc does not reach to the cord; R of 

 f orewing sinuate at origin of Rs; supra-anal 

 process normally reaches to middle of ninth 

 tergite; eastern species vernalis 



11. Seventh abdominal tergite with a raised knob or 



button 12 



Seventh abdominal tergite smooth, without a 

 raised knob or button •_ 14 



12. Ninth abdominal tergite with two distinct gran- 



ulate tubercles, one each side of the median de- 

 pressed area; supra-anal process short, glo- 



