PLECOPTERA NYMPHS OF NORTH AMERICA = 37 
rounded; front and hind margins nearly straight, sides flaring ; 
dises of pronotum somewhat rugose; lighter areas on lateral 
margins, as well as near the front and posterior median areas. 
Meso- and metanotum likewise with lighter spots. Legs brown ; 
tips of femora and the tarsi lighter; femora and tibiae with a 
fringe of whitish hairs. 
Abdomen eylindrie, brown, with three more or less distinct 
longitudinal stripes on the dorsum, one in the center and one on 
each side along the median area of the lateral fields; tenth ter- 
cite produced into a triangular process in both sexes. Cerei com- 
posed of some twenty-five segments. 
The gills are arranged as in Pt. badia but the individual fila- 
ments of the tufts are shorter than in badua. 
In the maturer nymphs, the genital characters, especially the 
genital plate of the female, can often be observed underneath 
the nymphal chitin, and thus specific identification becomes very 
simple. 
I have two juvenile forms from Estes Park, Colorado, which 
probably belong to this species, although the specimens differ 
much in appearance and structure from mature nymphs of either 
badia or regularis. One of these nymphs is only 3.5 mm. long. 
The most striking feature of this specimen is its spiny body. 
The femora and tibiae are covered with large spines, as are also 
the lateral margins of the meso- and metanotum and the abdom- 
inal segments. There are only nine pairs of gills, and these are 
located as follows: one pair anterior, and two pairs posterior to 
the prothoracic legs; one pair between, and one pair posterior 
to the mesothoracie legs, and one pair on each of the first three 
abdominal segments. The antennae are composed of fifteen seg- 
ments, and the cerei of thirteen segments. 
The second juvenile form measures 6.5 mm. in length, and 
resembles the smaller specimen in that the legs are covered 
with large spines. However, the spines on the thorax and the 
abdomen are fewer in number; the antennae are composed of 
twenty-eight segments and the cerci of sixteen segments. In 
this specimen there are ten pairs of gills distributed as in the 
smaller specimen except that there are two pairs anterior to 
the prothoracic legs, instead of one pair as in the smaller form. 
Inasmuch as these two specimens were collected in the same 
locality and at the same time as the mature nymphs of Piero- 
narcella regularis, it seems very probable that they are the same 
species. Furthermore, it would indicate that the life cycle of this 
species occupies two years. 
