ie THOMAS SAY FOUNDATION 
low and the caudal half brown; last segment yellow except for a 
small, basal, median brown spot; surface hairy, each segment with 
a fringe of short hairs on the posterior margin. Cerci yellow, of 
about twenty-two segments, each segment ending in a whorl of 
short hairs. 
Described from reared specimens, May 19 to 381, 1926, Ithaca, 
N.Y. | 
Genus PERLESTA Banks 
The nymphs of this genus resemble the nymphs of Perla but 
the segments of the cerci are longer in Perlesta than in Perla. The 
body is generally covered with small brown spots, giving the 
nymphs a freckled appearance. 
Length of the full-grown nymphs is about 10 mm.; color yel- 
lowish to yellowish brown, usually with a darker transverse band 
between the eyes, crossing the ocellar triangle; head a little nar- 
rower than pronotum; eyes moderately large; three ocelli ar- 
ranged in an isosceles triangle with the hind ocelli closer to each 
other than to the eyes; occipital ridge noticeable, although not as 
prominent as in most of the species of Perla. Antennae of medium 
length and composed of approximately fifty segments. Pronotum 
transversely oval, sides broadly rounded; surface quite smooth 
and lateral margins somewhat produced in the form of flattened 
flanges ; meso- and metanotum large, wing pads broad. Abdomen 
somewhat flattened, posterior margins of segments fringed with 
medium-sized spinules. Legs flattened, hairy, with long fringes 
of hairs on the outer margin of the femora and tibiae; first and 
second tarsal segments short, subequal, and together less than 
half as long as the third; cerci very long, about four-fifths as long 
as body with the segments beyond the middle four to five times 
as long as wide; each segment terminating in a whorl of long 
hairs. 
Seven pairs or groups of branched filamentous gills. Entire 
surface of body covered with long hairs, more noticeable in the 
younger specimens than in the fully mature ones. 
Mouth parts. Labrum about four times as wide as long, the an-. 
terior margin fringed with hairs. Mandibles asymmetrical, each 
with five sharp teeth followed by a series of long hairs. Maxillae 
rather long and slender; lacinia unique in that the inner margin 
below the large terminal tooth is devoid of a series of hairs, ex- 
cept for one long hair at the base of the second tooth, which is 
very long; galea very slender, extending about to the middle of 
the terminal tooth; tip of galea bearing a small bunch of hairs; 
