48 THOMAS SAY FOUNDATION 
them; labrum dark brown; antennae yellowish, about half as 
long as the body and composed of about eighty-five segments. 
Pronotum nearly twice as wide as long, slightly widened pos- 
teriorly; hind angles more broadly rounded than front ones; 
front margin a little convex, hind margin slightly concave in the 
middle; surface covered with fine hairs; margin bordered with 
short spinules; marginal groove more distinct on front and hind 
border than on lateral margins. Meso- and metanotum and wing 
pads covered with fine hair, and the margins of the wing pads 
with fine spimules. Legs flattened; femora with a dark blotch 
or transverse band at the basal and distal ends; legs with a 
thick fringe of long whitish hair on the outer margin. 
Abdomen flattened; basal half of tergites one to nine yellowish, 
the posterior half brown or blackish; the tenth tergite brown or 
blackish at the base and at the sides but with the central apical 
portion yellowish. The extent of the darker color varies consider- 
ably but even in the darkest specimens, in which almost the 
entire tergites are brown or blackish, the tenth tergite is yellow- 
ish at the apex. Dorsum of abdomen pilose, each tergite bearing 
on the posterior.margin a fringe of short spinules. Cerci reddish 
brown, about two-thirds as long as the body and composed of 
about fifty-five segments, each segment terminating in a whorl 
of short spines. Ventral surface of abdomen yellow except for 
a little brown on the abdominal segments, especially the posterior 
ones. : 
Eight pairs of bunched tracheal gills, arranged as in P. 1m- 
marginata, except that the nymphs of P. capitata possess, in 
addition to the thoracic gills, one pair of caudal gills which are 
attached to the subanal lobes between the cerci. The mouth parts 
do not differ materially from those described under P. immar- 
ginata. | 
New York: Ithaca; Dansville; Boquet R., Adirondack Mts.; 
Oneida Co.; Potomae R., Brunswick, Md.; Harper’s Ferry, 
W.Va.; Plummer’s Island, Md.; Guelph, Ont. 
Perla media Walker 
(Plate 16, fig. 190; plate 33, fig. 228.) 
Length of body up to 22 mm.; antennae up to 10 mm.; cerei 
up to 14 mm. 
The general color of these nymphs is yellowish brown to dark 
brown or almost black. The immature nymphs are generally al- 
most uniformly brown, with a coating of long fluffy hairs on the 
