3G III O.MAS SAY FOUNDATION 



its middle portion by darker markings that extend across 

 the disc. Trochanters yellowish and knees yellow in some 

 specimens. Veins of the wings blackish and somewhat 

 clouded. Abdomen pale yellow beneath. 



Male. The ninth ventral segment prolonged rearward, 

 covering and extending far beyond the 10th sternite, and 

 forming a broad, trough-like lobe that bears a median 

 straight-sided terminal notch. Segment 10 narrow below 

 where covered by 9, but elongated rearward on the dorsal 

 side and bifid into two long appendage-like lobes whose 

 opposed edges are emarginate in their apical half and 

 whose tips are strongly bent upward. Supra-anal plate de- 

 veloped as a sperm conveyor, unbranched, and with ter- 

 minal eversible sperm cup. Sup-anal plates elongate, 

 their tips projecting beyond the apex of the 9th sternite. 



Female. The eighth sternite, truncate apically and not 

 prolonged and showing no special demarcation of a sub- 

 genital plate. Normally the border is straight, but many 

 abnormalities occur owing to wrinkling in drying. The 

 soft lateral margins of the genital aperture may dry in 

 such a way as to form a minute triangle on either side, 

 the presence of which is responsible for at least one syn- 

 onym. 



Distribution. — Ohio River at Pittsburgh ; Maine to D. 

 C, to Tenn. ; to Kan. ; to Minn. ; to Saskatchewan ; to Alas- 

 ka and Labrador. Common in small rivers of the central 

 states where the nymphs live in the trash of the eddies 

 below stony rapids. 



Pteronarcys nobilis Hagen. 



(Plate 7, figs. 3, 4.) 



1861. Pteronarcys nobilis Hagen. Syn. Neuropt. X. A., p. To. $ 

 3873. Pteronarcys pictetii Hagen, Proc. Bost. Soe. Nat. Hist., 



15:286. 5 

 1917. Pteronarcys nobilis Smith, Trans. Am. Ent. Sop., 43:44S (con- 

 tains full synonomy. 10 titles). 



Male. Length to wing tips 31-34 mm. ; of tails 12 mm. ; 

 expanse of wings 55-57 mm. 



Female. Length to wing tips 45-48 mm. ; of tails 11 

 mm. ; expanse of wings 80-84 mm. 



Color uniform dark brown above, obscure orange be- 

 neath, excepting the tip of the abdomen which is often 

 shiny black beneath. There are often lateral apical spots 

 of orange or rufous on the abdominal tergites. Wings 

 smoky brown with darker veins. Inconspicuous yellow- 



