PLECOPTERA OF NORTH AMERICA 223 



Genotype, Leuctra geniculates Steph., European. 

 Distribution. — Generally distributed over the United 

 States and Canada. 



Key to the Species of Leuctra. 



Males. 



1. Cerci modified into large, chitinized, accessory 



copulatory organs, armed with hooks or spines 2 

 Cerci unarmed 3 



2. Subgenital plate deeply emarginate behind; 



probe (modified subanal lobes) slender, with a 



large membranous bulb at tip bradleyi 



Subgenital plate only slightly emarginate behind, 



probe not enlarged into a bulb at tip 



occidentalis 



3. Seventh and eighth abdominal tergites smooth, 



titillators either absent, or when present, re- 

 curved upon the abdomen and not in close prox- 

 imity to the subanal lobes 4 



Either the seventh or eighth abdominal tergites, 

 or both, with raised chitinous plates or proc- 

 esses except decepta which seems to vary consid- 

 erably in this character ; titillators always pres- 

 ent and lying in close proximity to the subanal 

 lobes 5 



4. Titillators and ventral lobe absent glabra 



Titillators and ventral lobe present, the former 



recurved ; subanal lobes sword-shaped ; cerci at 

 least four times as long as wide 



5. Seventh and eighth abdominal tergites each with 



two short raised triangular chitinous processes 



duplicata 



Not so 6 



6. Only the seventh tergite with raised chitinous 



process 7 



Only the eighth tergite with raised chitinous 

 process 10 



7. Chitinous process of seventh tergite long, slen- 



der, truncate, much longer than wide and reach- 

 ing across entire seventh tergite and well upon 



the eighth tenuis 



Chitinous process of seventh tergite short, wide, 

 as wide or wider than long 8 



8. Chitinous process of seventh tergite much wider 



than long, hind margin rounded; reaching not 



