482 
NORTH AMERICAN PLECOPTERA 
length of the body. Palpi pale brown; under side of head whitish except lateral 
borders of mentum which are brown. Meso- and metanotum dark brown with 
a narrow, yellow median line on the anterior border; the entire thorax pale 
beneath with a median, dark brown, shield-shaped spot between the base of 
the legs, on each side of the three segments, and just anterior to the median 
spots a dark brown, transverse band on meso- and metathorax. Legs yellow 
brown, femora rather dark, knees pale, darker bands at base and tip of tibiae, 
and tip of tarsi. 
Ocelli small, arranged in an isosceles triangle, the base of which is almost 
half again as great as the sides, the distance from the inner margin of the eye 
to the posterior ocelli less than the distance between the anterior and posterior 
ocelli. On either side of the ocellar triangle a glossy, kidney-shaj)ed tubercle, 
placed a little nearer the posterioi ocelli than the inner margin of the eyes. 
Pronotum broader than long, about as wide as the occiput, sides straight, 
anterior and posterior borders slightly convex, corners blunt; a broad, median 
yellow band somewhat widened anteriorly and posteriorly, the lateral fields 
dark with indistinct sculpturings on the inner half. Wings rather short, in the 
male “the anterior ones reach the posterior border of the seventh segment and 
the posterior ones, the posterior border of the eighth segment” (Klapdlek); in 
the female they just reach the tip of the abdomen; their color, browm; venation 
brown, except costa and base of subcosta which are yellowish; a scanty net- 
work of cross- veins in the apical part of the wing in the region before media; 
a little less than the first half of the costal area beyond the humeral cross-vein, 
free from cross-veins; the length of the inner inter-radial cell three times as 
great as its base. A single pair of slender, white, finger-like, tracheal gills 
widely separated on the base of the submen turn. 
Male. Klapdlek says that Arcynopteryx americana is normally developed 
and that there is no departure from the generic type (fig. 54). 
Female. Abdomen dark brown above and on the sides, pale on the venter. 
Setae slender, tapering, about half as long as the body; alternately yellow and 
dark brown, the apical half of the segment being the darker. The subgenital 
plate, truncate, about three-quarters as wide as the segment, scarcely pro- 
duced beyond the margin of the segment but distinctly marked off from it by 
dark browm, oblique corners, or, in one specimen, slightly rounded corners. 
The tenth tergite triangularly produced; the supra-anal plate a fleshy rounded 
lobe attached to the ventral surface of the tenth tergite; the sub-anal plates 
triangular, broadly divergent (fig. 55). 
We have two female specimens, one bearing simply the label, 
Wyoming, and the other (which has a more nearly dark brown 
general coloration than chestnut brown) from Little Laramie 
Liver, Hatton, Wyoming, V, 25, 1912. 
Nymph unknown. 
