154 THOMAS SAY FOUNDATION 



margin ; subanal lobes sharp, recurved upon the tenth 

 tergite ; supra-anal process not developed. 



Female. Subgenital plate of eighth abdominal sternite 

 very little produced, truncate or slightly rounded, entire. 



Distribution. — Type, female, No. 10822, June 22, Vin- 

 yard, Utah (Banks Collection, Mus. Comp. Zool, Cam- 

 bridge, Mass.). 



Isoperla bilineata Say. 



(Plate 14, fig. 2; plate 26, figs. 9, 10, 12, and text fig. 6.) 



1823. Sialis bilineata Say, Godman's West. Qnar. Kep.. 2:165. 



1833. Perla bilineata Newman, Ent. Mag., 5:499. 



1842. Perla bilineata Pictet, Ins. Neurop., p. 283. 



1859. Perla bilineata Le Conte, Ed. T, p. 175. 



1861. Perla bilineata Hagen, Ins. Neurop. N. A., p. 30. 



1862. Perla bilineata Walsh, Proc. Acad. Nat. Sci. Phil., p. 366. 

 1883. Perla bilineata Provancher, Pet. Faun. Can. Neurop., p. 74. 

 1892. Perla bilineata Banks, Cat., p. 342. 



1906. Isoperla bilineata Banks, Ent. News, 17:175. 



1907. Isoperla bilineata Banks, Cat. Neurop., p. 13. 



1907. Isoperla bilineata Tucker, Kans. Univ. Sci. Bull., 4:78. 



Length to tip of wings, male, 10-12 mm. ; female, 11-14 

 mm. Expanse, male, 18-22 mm. ; female, 20-26 mm. 



General color yellowish with greenish hyaline wings. 



Head a little wider than prothorax ; yellow with a brown 

 spot over the ocellar triangle, sometimes the spot is tri- 

 angularly emarginate behind so that the ocelli are con- 

 nected by a broad V-shaped dark mark ; a little darker on 

 clypeus ; lateral tubercles and frontal ridge not promi- 

 nent; hind ocelli a little closer to the eyes than to each 

 other. Antennae yellowish brown, darker toward the tip. 



Prothorax wider than long ; slightly, if at all, narrowed 

 behind ; sides straight ; angles almost square ; brown with 

 a broad median yellow stripe ; and sometimes with yellow 

 on the outer lateral margin ; surface not very rugose. Legs 

 yellowish, tarsi darker. Wings greenish or yellowish hy- 

 aline, veins brown ; subcosta does not reach to the cord ; 

 a series of costal crossveins before the end of subcosta 

 and one beyond. 



Abdomen and tails yellowish, the tails a little darker 

 towards the tip. 



Male. Ninth abdominal sternite much produced and 

 evenly rounded behind ; hind margin of eighth sternite 

 with a median knob which is as long as wide ; subanal lobes 

 recurved, bluntly pointed ; supra-anal process not de- 

 veloped. 



Female. Subgenital plate triangularly produced and 

 normally extending entirely across the ninth sternite. 



Distribution. — Ohio River, near Cincinnati; Newfound- 

 land to Saskatchewan and New Jersey to Colorado. The 

 common eastern species. 



