PLECOPTERA OF XORTH AMERICA 61 



regular network of crossveins between costa and the 

 branches of the radial sector ; nearly the first half of the 

 costal area beyond the humeral crossvein free from 

 crossveins ; the length of the inner inter-radial cell three 

 times as great as its base. A single pair of small, white, 

 fleshy, finger-like gills on the lateral margins of the sub- 

 mentum. 



Female. Abdomen uniformly dark brown ; basal seg- 

 ments of the setae brown, the following ones alternately 

 ringed with white and brown, each segment being marked 

 with a narrow, basal, ring of white followed by first a 

 narrow brown, then a narrow white band and finally a 

 broad, brown, terminal ring. Subgenital plate trapezoidal 

 with a broad, shallow, V-shaped, apical notch (fig. 48) . 



Distribution. — Old Forge, N. Y. (the female type), Aug. 

 16, 1905. (J. G. N.) 



Perlodes americana Klapalek. 



(Plate 7, fig. 21 ; plate 10, fig-. 5.) 

 1912. Arcynopteryx americana Kip., Coll. Zool. Selys., 4:21. 

 1917. Arcynopteryx americana Smith, Trans. Amer. Ent. Soc, 43:481. 



Expanse of wings, male 24 mm. ; female 37 mm. 



Color black, lineate with yellow. A broad longitudinal 

 mid-dorsal stripe begins between the ocelli and extends 

 along head and prothorax and ends in a triangle on the 

 praescutum of the mesothorax. Sometimes it is followed 

 by a narrow linear dash- on the top of the metathorax. 

 Hind angles of the head behind the eyes yellow, this being 

 confluent around the occiput with the middorsal stripe. 

 Frontal tubercles low, ovoid in outline, more or less yel- 

 low, in areas of solid black. The M-line on the frons is 

 dilated at its ends to cover the flaring lateral margins of 

 the clypeus. Antennae and palpi blackish. Legs obscure 

 brownish or translucent olivaceous, indistinctly darkened 

 toward the knees. Abdomen blackish, paler beneath. Tails 

 long, hairy, the segments darkened in color toward their 

 tips. 



Male. The apical carinae of abdominal segments 4 to 8 

 tend to become swollen and padlike rather than carinate, 

 and are covered with scurfy hairs on the dorso-lateral 

 angles. They are most thickened on segment 7. Segment 

 9 is narrower and generally pale, very much widened ven- 

 trally, the sternum is suddenly prolonged backward into a 

 wide ovoid subgenital scoop half as long as the portion of 

 the segment before it. There is a depressed area in the. 

 middle of the tergum of segment 9, and a bare callosity 



