480 
NORTH AMERICAN PLECOPTERA 
small, round, inconspicuous tubercles situated nearer the posterior ocelli than 
the inner margin of the eyes. The lateral borders of the clypeus pale yellow; a 
dark fuscous crown spot in the form of a letter X with its center in the median 
ocellus, the anterior part outlining the middle region of the M and the poste- 
rior part extending back to the lateral ocelli; a median, deep yellow, occipital 
spot reaching forward between the ocelli; dark brown, coarsely sculptured, 
oval-shaped spots on the lateral occipital areas. Antennae brown, the basal 
segment the darkest; under side of head pale, palpi dark brown. 
Pronotum rectangular, not as broad as the head; sides straight, front and 
hind margins convex, angles blunt; 9 , yellow median band, broader behind; 
the inner regions of the lateral fields with embossed markings. Meso- and 
metanotum and the entire venter of the thorax, with the exception of narrow 
areas surrounding the bases of the legs which are paler, dark brown. Legs 
brown except a pale band before the knees and pale tibiae. Wings with yellow- 
brown venation, except basal portions of costa and sub-costa in fore-wing and 
all bases in hind wing which are yellow; an irregular network of cross-veins 
extending from costa through the anterior branches of the sector, the network 
richest between radiusi and radius 2 , over the first half of the costal area beyond 
the humeral cross- vein free from cross-veins; the length of the inner inter- 
radial cell twice as great as its base. Without gills. 
Female. Abdomen uniformly dark brown, setae long and slender; alter- 
nately ringed with dark brown and white, except for the first few basal seg- 
ments, which have but a single ring of dark and light, each segment is marked 
with a white basal band followed first by a narrow brown, then a narrow white 
ring, and finally a broad brown one. The eighth ventral segment produced 
somewhat triangularly with a rectangular notch in the tip. Sub-anal plates, 
large, triangular (fig. 52). 
Described from a single specimen, the type, without locality 
label, in the collection of the Academy of Natural Sciences of 
Philadelphia. 
Male unknown. 
Nymph unknown. 
Arcynopteryx inornata new species 
Adult 
9 . — Length to tip of wings, 17 mm.; expanse of wings, 30 mm. 
Of an almost uniform dark brown coloration. Head rather triangular, so 
perfectly concolorous that the M-shaped mark, ocelli and tubercles are scarcely 
visible; palpi and under side of head also dark brown; basal segment of antennae 
dark brown, succeeding segments slightly paler. 
Pronotum trapezoidal, a Httle broader posteriorly, and the anterior border 
a trifle wider than the occiput, sides straight, front and hind margins shghtly 
arcuated, angles squarish; a broad, median, yellow band, lateral fields with a 
few coarse embossings. Meso- and metanotum, dark brown, also the entire 
venter of the thorax, except for small, pale areas around the bases of the legs. 
Legs yellowish brown. 
