102 THOMAS SAY FOUNDATION 



front margin convex. Rugosities rather strong, pattern 

 irregular. Meso- and metathorax brown, the former with 

 a pale spot at the front. Legs brown, lighter underneath, 

 with tarsi darker. Wings very broad, uniformly subhy- 

 aline. Veins few and interspaces are wide. 



Abdomen yellowish brown, darker toward the tip, un- 

 derneath yellowish except the last three segments. * Tails 

 brown, covered with fine, short pubescence. 



Female. Subgenital plate of the female little devel- 

 oped, the apex of the 8th sternite scarcely produced, its 

 margin soft and varying in form according to the extent 

 of contractions, normally straight but frequently a little 

 infolded in the middle in a wide apical notch. 



Male unknown. 



Distribution. — Known only from the type locality, which 

 is Yakima, Wash. 



Perla immarginata Say. 



(Plate 19, figs. 7-10; plate 13, fig. 2.) 



1823. Perla immarginata Say, Godman's West. Quart. Rept., 2:164. 



1861. Perla immarginata Ilagen, Syn. Neurop. N. A., p. 20. 



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



1907. Perla immarginata Banks, Cat. Neurop., p. 1. 



1908. Perla immarginata Banks, Proc. Ent. Soe. Wash., 9:150. 

 190S. Perla immarginata Banks, Trans. Ainer. Ent. Soe., 34:257. 



1909. Perla immarginata Klap. Bull. Acad. Boh., 14:13. 

 1913. Perla immarginata Smith, Ann. Ent. Soe. Am. 

 1902. Perla fumosa Banks, Can. Ent., 34:123. 



1907. Perla fumosa Banks, Cat. Neurop., p. 11. 



Length to tip of wings, male, 24-30 mm. ; female, 35-39 

 mm. Expanse, male, 42-50 mm. ; female, 62-68 mm. 



General color dark brown, varied with yellow. 



Head a little wider than prothorax, dark brown to 

 blackish over the ocellar triangle and with black on the 

 inside of the ocelli ; lateral tubercles large, with a de- 

 pression in the center ; frontal ridge not prominent ; occi- 

 put yellowish ; hind ocelli a little closer to each other than 

 to the eyes, especially in the female ; antennae dark brown 

 to blackish. 



Prothorax brown to blackish ; wider than long, consid- 

 erably narrowed behind ; disc quite rugose ; angles rather 

 sharp. Legs brown to blackish. Wings subf umose ; veins 

 dark brown; subcosta ends just beyond the cord; many 

 costal crossveins before the end of subcosta as well as 

 beyond. 



Abdomen yellowish ; tails yellowish at base, darker to- 

 wards the tip, closely beset with short hairs. 



