84 THOMAS SAY FOUNDATION 
copious fringes of hairs on the inner side of the cerci, in which 
considerable silt and dirt collect, gives the nymphs a rather 
unique appearance and is an aid in identifying them in the field. 
The nymphs are, of course, carnivorous in habit, and they ap- 
parently have a three-year life cycle. In some of the specimens 
which have been collected around Ithaca, I have found on the 
wing pads, and on the legs, small Chironomidae larvae. Whether 
these larvae are parasitic upon the nymph has not been definitely 
established, but it appears that this is not a mere accidental as- 
sociation, and that possibly these larvae may, to some extent, at 
least, be parasitic upon the stonefly nymphs. 
Ithaca, N.Y.; Moffitsville, N.Y.; Potomac R., near Harper’s 
Ferry, Md. 
Acroneuria arenosa Pictet 
Length of body up to 24 mm.; antennae up to 15 mm.; cerci 
up to 24 mm. 
This genus is represented in our collection by a single speci- 
men, collected from the Potomac River at Great Falls, Virginia, 
April 10, 1926. Identification was made possible by a study of the 
venation of the wing pads, which were far enough developed to 
clearly indicate the peculiarly much-branched condition of the 
anal veins of the front wings, a condition unique to this species. 
Nymphs rather strikingly patterned with yellow and brown. 
Head a little narrower than pronotum, the area posterior to the 
epicranial suture mostly yellow, with the portions behind the 
eyes darker brown; clypeus, frontal M-line, and a spot on the 
outside of each hind ocellus, yellow, remainder dark brown. Hind 
ocelli nearly twice as close to each other as to the eyes. Antennae 
yellowish, with about one hundred segments. 
Pronotum nearly twice as wide as long, dises and lateral mar- 
gins yellow, the rest dark brown; front margin fairly convex; 
hind margin slightly concave in center; angles broadly rounded ; 
surface nearly smooth and covered with a fine coating of hair. 
Meso- and metanotum patterned with yellow and brown, outer 
portions of wing pads brown, inner portions yellowish. 
Legs quite uniformly yellowish, with a median, longitudinal, 
narrow smooth line on the dorsal surface of the femora; margins 
of legs with a thick fringe of whitish hairs. 
Abdominal segments brownish, with a row of roundish, yellow 
spots along the median dorsal line, and with similar spots on 
the lateral margin of the posterior segments. Posterior margin 
of last abdominal tergite dark brown or blackish. In this respect 
