PLECOPTEKA OF NORTH AMERICA 201 



process with spines below venusta 



Wings without many clear rounded spots 21 



21. At the base of each cercus is a backward pointing 



chitinized spine-like process 22 



Base of cercus either with a membranous process, 

 a bluntly chitinized process or else smooth, 

 never a sharp chitinized spine-like process 23 



22. Spine-like process at base of cercus directed 



backward and about as long as cercus ; supra- 

 anal process (dorsal view) not much enlarged 



beyond base cornuta 



Spine-like process at base of cercus directed in- 

 ward and much shorter than cercus ; supra-anal 

 process (dorsal view) much enlarged beyond 

 base California) 



23. At base of cercus a large asymmetrical chitinized 



lobe directed backward and inward depressa 



No such blunt chitinized lobe at base of cercus 24 



24. At base of cercus a membranous rounded or 



elongate lobe 25 



No lobe at base of cercus 27 



25. Membranous lobe at base of cercus rounded ; sub- 



anal lobes neither bifurcate at tip nor pro- 

 duced into slender flexuous processes 



• color a dcnsis 



Membranous lobe at base of cercus elongate and 

 pointing inward ; subanal lobes either bifurcate 

 at tip or produced into slender flexuous proc- 

 esses 26 



26. Subanal lobes ending in slender flexuous proc- 



esses flexura 



Subanal lobes bifurcate at tip and not ending in 

 slender flexuous processes biloba 



27. Supra-anal process smooth, subanal lobes divided 



into two narrow sinuate chitinized bands, the 



outer one bearing heavy spines near the top 



sinuata 



Supra-anal process spinulose either above or be- 

 low; subanal lobes not very slender and not 

 armed with heavy spines 28 



28. Supra-anal process with spines below, subanal 



lobes divided longitudinally, each half bearing 



groups of heavy hairs venosa 



Supra-anal process finely spinulate above; sub- 

 anal lobes much prolonged and deeply bifurcate 

 at tip bifurcata 



