PLECOPTERA OF NORTH AMERICA 



145 



Fig. 19. Isoperla 

 hilineata Say. 



developed subgenital plate. 

 Genotype, Sialis bilineata Say 



ish hyaline ; subcosta usually does 

 not reach the cord ; a series of costal 

 crossveins before the end of sub- 

 costa and from one to three cross- 

 veins beyond the end of subcosta; 

 radial sector forked once beyond the 

 cord ; hind wing with a large folded 

 anal area ; no series of cubital cross- 

 veins in hind wing. 



Abdomen with two long tails 

 whose middle segments are three to 

 five times as long as wide. 



Male. Ninth abdominal sternite 

 much produced so as to extend at 

 least to the tip of the abdomen ; 

 eighth sternite with a rounded, 

 thickened knob on the hind margin ; 

 subanal lobes modified into slender 

 upturned or recurved hooks ; tenth 

 tergite entire; supra-anal process 

 not developed. 



Female. Eighth abdominal ster- 

 nite either unmodified or with a well 



Key to the Species of Isoperla. 



Color blackish ; female subgenital plate somewhat 

 produced and broadly emarginate at tip ; penis 

 of male, when extruded, with two slender chi- 

 tinized processes below fusca 



Color greenish, yellowish or brownish 2 



Dark brown with very little yellow, prothorax al- 

 most twice as wide as long; less than 8 mm. in 

 length minuta 



Mostly yellowish ; if brown, with considerable yel- 

 low color on head and pronotum 3 



Head with a round yellow spot in the ocellar tri- 

 angle surrounded by dark brown ; pronotum 

 with a basal median yellow stripe and with 

 brown sides 4 



Head either almost concolorous or with a V- 

 shaped dark mark connecting the hind ocelli 

 with the front ocellus ; pronotum with a yellow 

 median stripe and with the lateral margins yel- 

 low 6 



