PLECOPTERA OF NORTH AMERICA 173 



General color brown to dark brown with the wings 

 lightly to heavily infuscated. 



Head much narrower than pronotum; yellowish to al- 

 most black (in some specimens yellow with a large me- 

 dian dark diffused area) ; ocelli small, much closer to each 

 other than to the eyes ; antennae brown to blackish, some- 

 what lighter at the base. 



Prothorax brown to blackish with the margins some- 

 times yellowish ; front margin concave, hind margin near- 

 ly straight, sides bulging out somewhat and a little nar- 

 rowed behind; much wider than long; front angles some- 

 what rounded ; hind angles almost sharp ; margins strong- 

 ly flaring; surface quite rugose. Legs brown, darker 

 above. Wings moderately to heavily infuscated, some- 

 times quite blackish ; veins dark brown to blackish ; sub- 

 costa reaches almost to the cord; 13-17 costal crossveins 

 before the end of subcosta and 4-9 beyond; radial sector 

 usually with 4-5 branches. 



Abdomen brownish, lighter underneath. Cerci brown 

 at the base, darker toward the tip, short and abruptly 

 tapering; basal segment a little shorter than the follow- 

 ing three segments. 



Male. Ninth abdominal sternite produced and evenly 

 rounded behind, bearing some distance forward from the 

 hind margin a narrow, transverse, rounded knob ; from 

 the sides of this knob two divergent ridges and the area 

 between these ridges sunken; tenth tergite triangular 

 with the tips upturned ; supra-anal lobe consists of a mem- 

 branous, globose lobe. 



Female. Hind margin of eighth abdominal sternite 

 produced into a broad subgenital plate which covers most 

 or all of the following segment, with a wide and shallow 

 apical emargination. 



Distribution. — Type, female, 1878, Reno, Nev. (Morri- 

 son, in the Mus. Comp. Zool., Cambridge, Mass.) ; four fe- 

 males, ten males, June 8-29, Shasta Springs, Calif. (C. L. 

 Fox and E. P. Van Duzee). 



Genus ACRONEURIA Pictet. 



1841. Acroneuria Pictet, Perlides, p. 144. 



1909. Acroneuria Klapalek, Bull. Internal;. Ac-ad. Sci. Boheme, pp. 

 1-14. 



Large stoneflies, 20-40 mm. in length {A. pumila Bks. is 

 somewhat smaller) . Head wider than pronotum, either 

 concolorous or with a dark area over the ocellar triangle 

 and over the clypeus ; frontal ridge in the form of a broad 



