PLECOPTERA NYMPHS OF NORTH AMERICA 73 
2. Caudal half of abdominal segments dark, and the basal half 
UL UGSO Lege Sala onk aa gegen signata (p. 75) 
Abdomen with a wide, median, longitudinal yellow stripe. 3 
3. Wing pads well developed; legs with fringes of long hairs... . 
RGM rte Octet acts, dds fo de hs 5-punctata (p. 74) 
Wing pads absent, i.e. the postero-lateral angles not pro- 
duced; legs without prominent hair fringes............. 
TT eet OTs ee Aap Pe Weds petersont (p. T4) 
Isoperla bilineata Say 
(Plate 8, figs. 123-128.) 
Length of body up to 10 mm.; antennae up to 5.5 mm.; cerci 
up to 5.5 mm. 
General color yellowish with dark brown markings. Easily 
recognized by three longitudinal dark stripes on the dorsum of 
the abdomen and by the color pattern of head and thorax. 
Head very little wider than pronotum, yellowish with dark 
brown to blackish markings varying somewhat in different in- 
dividuals. In the lighter specimens there is a wide, irregular, 
transverse, dark bar across the center of the head, extending from 
the base of one antenna to the other. In addition to this bar, there 
are darker markings in front of the clypeus, and dark blotches 
behind the posterior ocelli and back of the eyes. In the darker 
specimens, the entire head is almost uniformly brown except 
for a yellow spot in the ocellar triangle, another in front of the 
anterior ocellus, and a narrow one behind the ocellar triangle. The 
three ocelli are placed in an almost equilateral triangle, the hind 
ones being a little closer to the eyes than to each other; surface 
of head smooth and rather sparsely clothed with brown hairs; 
antennae composed of about forty segments. 
Pronotum about twice as wide as long; suboval; hind angles 
more broadly rounded than front ones. A wide, median, longi- 
tudinal yellow stripe; dise brownish; lateral margins yellow; 
marginal groove distinct along the anterior and posterior margins 
but indistinct on the lateral margins; surface nearly smooth 
and moderately covered with short brown hairs. 
Meso- and metanotum and wing pads yellowish with many 
irregular dark markings. Legs somewhat flattened, hairy, the 
femora and tibiae with a fringe of thin long hairs, more pro- 
nounced on the femora than on the tibiae. 
Abdomen yellowish, with three wide, dorsal, longitudinal dark 
stripes and in some specimens also with darker interrupted 
