PLECOPTERA NYMPHS OF NORTH AMERICA 91 
Head a little wider than pronotum ; a dark spot over the ocellar 
triangle except that in some nymphs there may be seen a small, 
round yellow spot in the middle of the ocellar triangle; hind 
ocelli much closer to each other than to the eyes; occipital ridge 
absent ; antennae less than half as long as body and composed of 
about eighty-five segments. 
Pronotum almost twice as wide as long, transversely oval; hind 
angles more broadly rounded than front ones; lateral flanges 
narrow, yellow; marginal groove distinct; surface thickly coated 
with brown hairs and the margin fringed with small spinules 
and a few longer hairs, especially on the posterior margin. Meso- 
and metanotum patterned with yellow and brown, and thickly 
coated with brown hairs. Legs flattened, and with a fringe of 
long white hairs. 
Abdomen moderately flattened; basal half of tergites usually 
darker than caudal half; posterior margins brown. Cerci at least 
half as long as body, each of the thirty-five segments terminating 
in a whorl! of spines. 
Gills arranged similarly to those of A. californica, but more 
copious, and the gill tufts at the base of the meso- and meta- 
thoracic legs are bunched so closely together that they appear as 
single tufts. 
The mouth parts are very similar in structure to the mouth 
parts of A. californica. 
Of this species I have several reared specimens from Yellow- 
stone National Park. 
