474 
NORTH AMERICAN PLECOPTERA 
Kockies, VII, 4, 1908 (Bradley), and two, one (long-winged) and 
one (shoit-winged), from Wyoming; also five females fall alco- 
holic), four from Rogers Pass, Selkirk Mountains, British 
Columbia, VIII, 1908 (Bradley), and one from Wyoming. 
Hagen gives September as the date of occurrence for the foot- 
hills of Colorado, and August 16 to September 6 for the moun- 
tains of the Pacific Slope. 
Type specimen of species in the Museum of Comparative 
Zoology, Cambridge, Mass. 
Nymph 
Immature nymphs. Length to tip of abdomen, 18 mm. 
Color, pale yellow-brown varied Mth yellowish markings. Head squarish, 
considerably broadened on the sides by enormous maxillae. Three small 
ocelli arranged in an isosceles triangle, the side of which is less than the base 
but equal to the distance from the inner margin of the eyes to the posterior 
ocelli. On either side of the ocellar triangle a pale yellow tubercle, a prominent 
M-shaped mark of the same color, the region anterior to the middle part of 
the M also pale, labrum and lateral portions of clypeus brown; lateral occipital 
areas with rather large, oval spots, in some specimens also a small, triangular 
median occipital spot and an indistinct one between the ocelli. Under side of 
head, palpi and antennae pale. 
Pronotum much narrower than the head, broader than long, anterior border 
straight; sides and posterior margin convex; front angles blunt, hind ones con- 
siderably rounded off; a narrow, pale j^ellow median line, inner halves of the 
lateral fields with pale sculpturings, meso- and metanotum similarly marked. 
The entire venter of the thorax pale yellow. Legs pale yellow, except for the 
dorsal aspects of the trochanters, coxae and femora which are brown; thick 
fringes of long, fine hair along the outer edges of the femora and tibiae. Four 
pairs of tracheal gills in the form of slender, finger-like, blind sacs situated as 
follows; one small pair far apart on the base of the submentum, the second 
pair, which is also small, on the latero-anterior border of the base of the front 
legs, the third and fourth pairs on the latero-anterior sub-marginal areas of 
the meso- and metasternum on a line with the inner borders of the base of 
the middle and hind legs (fig. 46). 
Abdomen brown above, yellow below. Setae pale yellow, each articulation 
surrounded by a whorl of short, stout, brown hairs, a thick fringe of long, fine 
hairs along the mid-dorsal line of each seta. The posterior border of the tenth 
tergite slightly produced; the supra-anal plate, a fleshy lobe attached to the 
ventral side of the posterior border of the last tergite (fig. 47, Sup. A. P.); 
sub-anal plates, triangular (fig. 47, Sub. A. P.). 
The general form and coloration of these nymphs indicates that they belong 
in this tribe, and since they agree with the adult Megarcys signala in size, num- 
ber, and location of the gills, I am placing them in that species tentatively. 
