PLECOPTERA OF NORTH AMERICA 31 



Key to the Families. 



1. Anal area of forewing with two or more full rows 



of crossveins Pteronarcidae 



Anal area of forewing either without crossveins or 

 when present there is only one row 2 



2. Well developed, many-segmented, cerci (tails) 



present 3 



Cerci one-segmented or much reduced-Xcnwwidac 



3. Forewings with a series of median and cubital 



crossveins; radius and media incompletely 

 fused and separating gradually at the base ex- 

 cept in small greenish forms Perlidae 



Forewings with only one or two median and one 

 cubital crossvein ; radius and media completely 

 fused at base and separating at a rather sharp 

 angle Capniidae 



V 



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