PLECOPTERA NYMPHS OF NORTH AMERICA — 39 
be recognized by a small median notch on the hind margin of 
the eighth abdominal sternite. 
The mouth parts are of the typical herbivorous type: labrum 
wider than long, densely covered with hairs, especially on the 
anterior margin; mandibles broad and asymmetrical, each man- 
dible with four or five unequal teeth followed by a broadened 
molar which is slightly hairy or spinulose, and beyond this a 
bunch of long hairs; maxillae broad; lacinia bidentate, the sec- 
ond tooth nearly as long as the first, followed by a row of long 
hairs; galea broad, flattened, somewhat hairy, and at the tip a 
bunch of rather long hairs; maxillary palpus considerably longer 
than the lacinia; labium with a large, wide submentum; men- 
tum a narrow transverse band; the glossae shorter than the para- 
glossae and beset with long hairs; the three-jointed labial pal- 
pus, when fully extended, reaches beyond the tip of. the para- 
elossae; hypopharynx rounded and produced normally to the 
tip of the glossae. 
The nymphs of this genus are herbivorous and are usually 
found in small fresh-water spring brooks where the current is 
quite slow, and where dead leaves and debris accumulate. In 
such localities Peltoperla may usually be found in considerable 
numbers. By collecting a handful of leaf-drift and sorting it 
carefully, one can usually find these roach-ike nymphs. P. arcu- 
ata, which is the most common species in the vicinity of Ithaca, 
apparently has a two-year life cycle. 
I have many nymphs collected from various localities, and all 
of these agree with the above generic description, but P. arcuata 
is the only species in the genus which has been reared to maturity. 
The other nymphs, I have been unable to identify to species. 
Peltoperla arcuata Needham 
(Plate 2, figs. 27-32; plate 12, figs. 183-184; plate 14, figs. 186-187.) 
Leneth of body up to 9 mm.; antennae up to 6.5 mm.; cerci 
up to 3 mm. 
General color chestnut-brown, with somewhat lighter areas on 
the prothorax, antennae, legs, and cerci. 
Because of the deflexed condition of the head, it appears to 
be very wide and short. The head is much narrower than the 
pronotum, and is bent over to such an extent that the clypeus and 
labrum are directed rearward underneath. The color of the head 
is uniformly brown except for a little lighter area around the 
compound eyes, which are black and rather small; epicranial 
suture very distinct; hind ocelli black, plainly visible, and about 
