LUCY WRIGHT SMITH 
463 
Pteronarcella nymph — “a” 
$. — Length of the body, 19 mm.; length of antennae, 9 mm.; length of 
setae, 7 mm. 
Blackish-brown with no conspicuous variation in color or markings except 
for the thick, white fringes of hair on the legs, and the white tracheal gills. 
Head very much narrower than the prothorax, ocelli inconspicuous; faint, 
round spots outside the ocellar triangle. Antennae slender, tapering, of about 
forty-five segments. 
Prothorax almost twice as broad as long, front and hind margins straight; 
sides, flaring, convex; angles rounded (fig. 38). Legs with heavy fringes of 
long, white hairs along the outer edge of the femur and tibia. 
Abdomen cylindric. Tracheal gills very conspicuous, each tuft composed 
of many rather stout, erect filaments. 
Female. The posterior margin of the eighth ventral segment with a median 
depression; the tenth segment narrow below, produced above into a triangular 
process ending in a straight, sharp spine; the supra-anal plate, a fleshy lobe 
attached ventrally to the anterior part of the tenth dorsal segment (fig. 36). 
Two female nymphs (alcoholic specimens), not quite mature, 
from Tvler Lake, Boulder, Colorado, III, 13, 1905. These 
nymphs are in the entomological collection at Cornell University. 
For the present this nymph is left unnamed, since it may belong 
to one of the Colorado species, Pteronarcella regularis or Pteronar- 
cella badia. 
PERLODINI 
A few years ago Klapdlek separated off from the Perlini, the 
genera Perlodes Banks, Isogenus Newman and a small part of 
Perla Geoffroy, under the name Perlodidae. This family contains 
a number of genera, some made by revision of the old ones, while 
others are entirely new. He has used venation and genitalia as 
primary characters for classification. As formerly, in the genera 
Perlodes and Isogenus, the chief venational character is tho 
apical network of cross-veins. Klapdlek recognizes two groups, 
one in which “there is present a more or less irregular network 
of cross-veins in the tip between R, its sector, and the branches 
of the latter, sometimes even to M, and from its posterior branch 
to the posterior margin”; and another group in which “the net- 
work is lacking and there is a single cross-vein between R and 
Rs.” 
Under the tribe Perlodini I am including those genera of 
Klapdlek’s family Perlodidae which have an apical net^^ork of 
TRANS. -AM. ENT. SOC., XLIII. 
