38 THOMAS SAY FOUNDATION 



Male. Ninth ventral segment little produced backward 

 and not entirely covering the 10th sternite and set off at 

 each side of the pleura by an impressed fold. Tenth tergite 

 deeply divided above into two erect bluntly rounded lobes. 

 Supra-anal plate developed as a corneous, and complicated 

 sperm conveyor. Its superior margin runs out to rear- 

 ward and ends in a free bifid tip; before this tip is a lat- 

 erally flattened ventrally directed branch, that bears the 

 sperm cup on its proximal side, just before an apical di- 

 latation ; subanal plates broad. 



Female. Eighth ventral segment bears just before its 

 apical margin two somewhat equilateral-triangular pro- 

 cesses whose tips reach the middle of segment 9. 



Distribution. — Montana to New Mexico and Washing- 

 ton to California, 



This is the common species of our western mountains, 

 where it is on the wing during June, July and August. The 

 easternmost specimen we have seen is also the earliest in 

 season, and was collected by G. A. Dean in Riley County, 

 Kansas, on April 25. 



Pteronarcys princeps Banks. 



(Plate 7, figs. 7, 8.) 

 1907. Pteronarcys princeps Banks, Can. Ent., 39:327. 

 ]907. Pteronarcys fumipennis Klapalek, Bull. Internal. Soc. Boh., 



p. 12 of reprint. 

 1917. Pteronarcys princeps Smith, Trans. Amer. Ent. Soc, 43:450. 



Male. Length to wing tips, 36 mm. ; of antennae, 21 

 mm. ; of tails, 7 mm. ; expanse of wings, 68 mm. 



Female. Length to wing tips, 47 mm. ; expanse, 83 mm. 



Color dark brown to blackish, darker than in other 

 species of the genus. Middorsal line on the disc of the 

 prothorax obscure reddish yellow, narrow or more or less 

 interrupted in the middle. Wing veins clouded with 

 blackish brown. Prothorax wider than long, about as 

 wide as the head. Straight margined on front and at 

 sides but convex behind, angles sharp. 



Male. Nint;h ventral segment moderately produced 

 rearward where broadly rounded and upcurving, covering 

 more than the 10th sternite, an impressed fold each side 

 as in P. caHforuica. Tenth segment a narrow ring, divided 

 on the dorsum into two erect narrow lobes. Supra-anal 

 plate developed into an enormous horny sperm conveyor, 

 the extreme of complexity, for this genus, more highly 

 arching than in P. calif 'arnica, its bifid tip more strongly 



