PLECOPTERA NYMPHS OF NORTH AMERICA 85 
it resembles lycorias somewhat, but this dark band is narrower in 
arenosa. Cerci yellowish, with a rather thin fringe of hair on the 
inner margin; composed of about sixty segments, each segment 
terminating in a whorl of short spines. 
Gills very similar in size and location to those of abnormis, 
however, arenosa possesses a pair of small caudal gills in addition 
to the thoracic ones. 
Nothing is known of the life history of this species, although 
the mouthparts indicate that it is carnivorous in habits, and the 
general structure suggests that it normally inhabits the larger 
swift-water streams. 
Potomac River at Great Falls, Va. 
Acroneuria californica Banks 
(Plate 26, fig. 205.) 
Length of body up to 24 mm.; antennae up to 10.5 mm.; cercei 
up to 14 mm. 
General color yellow and brown; entire body thickly covered 
with short brown hair. The yellow spot over the ocellar triangle 
serves as a good identification mark of this species. This yellow 
spot is bounded on the rear by the arms of the epicranial suture, 
extends laterally beyond the hind ocelli to a sharp point, and 
reaches anteriorly almost to the front ocellus. Hind ocelli much 
closer to each other than to the eyes; occipital ridge faintly indi- 
cated by a row of spinules, especially in the center of the occiput. 
Entire surface of head thickly covered with short brown hair, 
usually more noticeable on the darker areas; antennae nearly 
half as long as body and made up of about eighty segments. 
Pronotum a little narrower than head, slightly widened posteri- 
orly; front and hind margins convex; hind angles more broadly 
rounded than front ones; marginal groove distinct ; lateral flanges 
narrow and yellow; median longitudinal yellow line narrow. 
Meso- and metanotum and wing pads covered with hairs, and on 
the outer margins with short spinules. 
Legs flattened ; with a fringe of long hairs on the outer margin. 
Abdomen not much flattened, yellowish but with the posterior 
margins of the tergites brown, covered with brown hairs and 
the posterior margins of the tergites with a fringe of spinules. 
Cerci about half as long as the body and composed of about 
thirty-five segments, each segment ending in a whorl of spines. 
Nine pairs of gill tufts; two pairs at the outer base of the 
prothoracie legs; two pairs in similar locations on the meso- 
