484 
NORTH AMERICAN PLECOPTERA 
“This species is certainly very near Arcynopteryx compacta Mac Lachlan, 
but is distinguished by its darker color and smaller body.” Translation from 
Klapdlek. 
Unknown to us. 
Nymph unknown. 
Arcynopteryx nymph — “b” 
Immature n 3 unph. Length to tip of abdomen, 22 mm.; length 
of antennae, 12 mm. 
Distribution .- — Las Vegas, New Mexico. 
Color, yellowish brown, varied wdth paler markings. Head squarish, three 
small ocelli placed in an isosceles triangle, the base of which is about a third 
greater than sides, and equal to the distance between the inner margin of the 
eyes and the paired ocelli. Tubercles pale yellow, kidney-shaped; the M- 
shaped mark prominent, also pale yellow; a small median triangular pale 
spot confluent with the middle portion of the M ; labrum and anterior border 
of the clypeus, white; pale yellow, oval-shaped spots on the lateral occipital 
areas; a faint indication of a median, occipital, triangular yellow spot reaching 
forward between the ocelli. Under side of head, palpi and antennae, pale 
yellow. 
Pronotum as broad as the occiput, nearly twice as wide as long, sides and 
both margins convex, angles rounded; a narrow, median, pale line, lateral 
margins bordered with pale yellow, the inner halves of the lateral fields with 
pale sculp turings, the meso- and metanotum with similar markings. The 
entire venter of the thorax pale yellow. Legs also pale yellow. The outer 
margins of the femora and tibiae with thin fringes of long, fine, silky hairs. 
A single pair of finger-like tracheal gills placed far apart on the base of the 
submentum. 
Abdomen brownish-yellow above, with three rows (a median one and on 
either side of it, a lateral one) of pale yellow spots, the spots on the last few 
segments are most conspicuous. The entire venter of abdomen and basal 
segments of the setae (all that remains of them) pale yellow. The tenth ter- 
gite triangularly produced; the supra-anal plate (fig. 57, Sup. A. P.) a rather 
large, fleshy lobe attached to the apical border of the last tergite; the sub-anal 
plates, (fig. 57, Sub. A. P.), triangular. 
I am placing nymph “B” in the genus Arcynopteryx since it 
possesses a single pair of gills of the same form and in the same 
location in which they occur in two species of the adults of the 
genus. 
Described from a single specimen from Las Vegas Hot Springs, 
New Mexico (T. D. A. Cockerell). 
We have two other ver^" >mung nymphs with a similar arrange- 
ment of gills but with different color patterns. They are too 
