40 THOMAS SAY FOUNDATION 



ferent in form and doubtless in function from thai of the 

 preceding species. No sperm cup present. 



Female. Oval subgenital plate occupying half of the 

 8th sternite and bearing at its apex a pair of long spine- 

 like processes that reach to the middle of the ninth ster- 

 nite. These processes are closely approximated at the 

 base, and after slight divergence, often again approxi- 

 mated at their tips. 



Distribution. — Trenton Falls and Ithaca, N. Y. ; Mass.; 

 Vt. ; Mackenzie River and N. Red River, Canada ; Cali- 

 fornia. 



The male and female associated together by Newman 

 in his original description of this species do not belong to 

 the same species. This was proved by Miss Lucy W. 

 Smith by the rearing of both sexes at Ithaca, N. Y. This 

 mixup led to the description of the true female of P. pro- 

 teus as P. spinosa. Nymphs abound in the spring fed brooks 

 about Ithaca, though the adult is rarely collected. 



Pteronarcys biloba Newman. 



(Plate 7, figs. 9, 10.) 

 1838. Pteronarcys biloba Newman, Ent. Mag., 5:176. 

 1876. Pteronarcys bicarinatus Provancher, Nat. Canad., 8:190. 

 1917. Pteronarcys biloba Smith, Trans. Am. Ent. Soe. 43:453 (full 

 bibliography of 9 titles). 



Male. Length to wing tips 34 mm.; expanse of wings 

 55 mm. 



Female. Length to wing tips 46 mm. ; expanse of 

 wings 84 mm. 



Color dark brown above and below. A narrow rufous 

 median line upon the prothorax; frontal cornicles rufous; 

 legs dark brown, paler at the knees. 



This is the handsomest species of the genus. In ma- 

 ture specimens the middle pale line on the pronotum is 

 rather bright red, as is also the whole ventral surface of 

 the body. The wings are marked by two clouds of fuscous, 

 one extending obliquely outward from the wing base 

 along the median cross veins, and the other extending 

 transversely backward from the region of the stigma. 



Male. Ninth ventral segment moderately produced, 

 covering segment 10 below, up-curving to a broadly 

 rounded and thickened rear margin. Segment 10 bifid 

 above, a wide cleft separating the two rounded lobes. Sub- 

 genital plates spoonshaped together clasping the base of 

 the supra-anal plate which forms, as in P. proteus, a slen- 

 der erect and recurving chitinous probe-like organ. 



