PLECOPTERA OF NORTH AMERICA 12.5 



Male. Tenth abdominal tergite cleft ; ninth tergite con- 

 siderably humped; supra-anal process short, with a flat- 

 tened rounded knob at the tip whose front margin is 

 finely serrate ; subanal lobes small, unmodified ; ninth ster- 

 nite produced and truncate behind. 



Female. Median portion of the hind margin of the 

 eighth abdominal sternite produced into a small triangu- 

 lar subgenital plate. 



Distribution. — Holotype male, allotype female, Aug. 5, 

 1923, Moraine Lake, Alberta, Canada (J. McDunnough, 

 in the Canadian Entomological Collection, Ottawa, Can- 

 ada). 



Paratypes, one male, two females, from the same lo- 

 cality ; one male, July 7, Waterton Lakes, Alberta, Canada 

 (J. McDunnough) ; two males, Aug. 9, 1905, Downie 

 Creek, Selkirk, Mts., B. C. (J. C. Bradley). 



Very similar to A. nanina Bks. 



Alloperla imbecilla Say. 



(Plate 20, figs. 1, 2.)) 

 1823. Sialis imbecilla Say, West. Quart. Rept., p. 165. 

 1861. Perla imbecilla Hagen, Syn. Neurop. X. A., p. 31. 



1906. Alloperla imbecilla Banks, Ent. News, 17:17.5. 



1907. Alloperla imbecilla Banks, Cat. Neurop., p. 13. 



Length to tip of wings, male, 8-9 mm. ; expanse, male, 

 13-15 mm. ; length to tip of wings, female, 9.5 mm. ; ex- 

 panse, female, 16 mm. ■ 



General color pale yellowish green. 



Head a little wider than prothorax; pale yellow; ocelli 

 black ; hind ocelli a little closer to eyes than to each other ; 

 antennae pale yellow. 



Prothorax a little wider than long; almost oval, the 

 front angles very broadly rounded, hind angles narrowly 

 rounded ; uniformly pale yellowish ; slightly rugose. Legs 

 pale yellow ; wings pale hyaline, veins pale. 



Abdomen pale yellowish, cerci pale yellow. 



Male. Tenth abdominal tergite bifid ; supra-anal process 

 recurved, slender, gradually tapering to a point, normally 

 reaching under the hind margin of the ninth tergite ; sub- 

 anal lobes small, unmodified; ninth abdominal sternite 

 produced and rounded behind. 



Female. Hind margin of eighth abdominal sternite 

 with the median portion produced into a narrow tongue- 

 like subgenital plate. 



Distribution.— Burton, Ga., May 21, 1911 (J. C. Brad- 

 ley) ; Newfield, N. Y., June 5 ; Sport Island, Sacandaga R., 



