96 THOMAS SAY FOUNDATION 
metanotum seem to be a little longer in this species than in 
N. sinuata but this difference is not sufficient to be of much aid 
in separating the species. In fully mature nymphs the developing 
genital structures are of considerable aid in identification. 
TthacayeN sy: 
Nemoura coloradensis Banks 
Length of body up to 6.8 mm.; antennae up to 4 (?) mm.; 
cerel up to 4 (?) mm. 
General color brown to dark brown. 
It is with some doubt that I include this species, for the nymphs 
before me have not been reared. However, they are mature and 
show the genital structures fairly well. The gills are present in 
the cervical region in four groups, with eight gill filaments in the 
outer group, and eight to nine in the inner group. The fringe of 
hairs on the pronotum, and the arrangement of the spines on the 
legs, are similar to N. sonwata. In the male nymphs the subanal 
lobes are large, somewhat subquadrate, and a little upturned. 
Nymphs from Bozeman, Mont. 
Nemoura sp. 
Among the collection of Nemoura nymphs, I have a number 
of aleoholic specimens from Colorado which differ markedly from 
any of the Nemowra nymphs described in this paper. 
In the cervical region, there are four single large finger-like 
gills. The legs are covered with spiny hairs, and on each of the 
femora, beyond the middle, there is a diagonal transverse row 
of long spine-like hairs. This row of spines is continuous in the 
femora of the pro-, and mesothoracic legs, but in the femora 
of the metathoracic legs the row of spines is interrupted by a 
gap. In other details these nymphs resemble other species within 
the genus. 
Genus LEUCTRA Stephens 
The nymphs of this genus are most readily recognized by the 
slender form of body and the shape and position of the wing 
pads. The wing pads are long and narrow and lie parallel with 
the body, the mesothoracic ones are set far apart at the base, while 
the metathoracic are set close together. 
General color yellowish brown to darker brown. Fully mature 
nymphs measure 10 mm. or less in body length. Antennae and 
cerci well developed, being normally about half as long as the 
body. 
