PLECOPTERA OF XORTH AMERICA 49 



6. Forewing with a branched vein from anal cell 



below; prothorax transversely oval i. e., angles 

 usually much rounded; mostly small greenish 



species 7 



Forewing with two simple veins from anal cell 

 below; prothorax squarish i. e., angles rather 

 well defined 9 



7. Hind wing without folded anal area and no wider 



than the forewing; small greenish species (un- 

 der 10 mm. in length) Ckloroperla 



Hind wing with a folded anal area and wider than 

 forewing 8 



8. Greenish forms ; Cu2 of forewing very short, sep- 



arating from Cul about opposite the tip of 1st 

 A and curving downward at a broad angle ; R 

 and M of forewing fused at base ; hind wing 



without intercubital crossveins Alloperla 



Not greenish ; Cu2 of forewing longer and sep- 

 arating from Cul nearer the origin of 1st A ; R 

 and M of forewing not fused at base ; hind wing 

 with intercubital crossveins Paraperla 



9. Portion of wing beyond the cord is short and at 



the front of the radial sector there is a network 



of irregular crossveins Pcrlodcs 



Portion of wing beyond the cord is longer and if 

 crossveins are present, not so localized (except 

 in Acroneuria they are few and regular) 10 



10. Radial sector with numerous branches that curve 



forward at tip. Tip of vein M curves back- 

 ward; large species with ocelli very small and 



wide apart Isogenics 



Tips of branches of vein Rs and M less divergent 11 



11. Hind wing without intercubital crossvein; mostly 



greenish species; male with an apical lobe be- 

 neath segment 8. Subgenital hooks slender, 

 claw-like, and developed from the subanal lobes 



, Isoperla 



Hind wing with several intercubital crossveins __ 12 



12. Costal edge of wing yellow including base of Rs 



and M. In hind wing Rs and M fused basally 

 more than half the length of the wing disc. 

 Middle segments of tails 3 to 5 times as long as 

 wide Perlesta 



