98 THOMAS SAY FOUNDATION 
been discovered which will separate the two above species or 
which distinguish them from L. claassent Frison, recently de- 
scribed by Frison (6). Identification can, therefore, at present 
be made only by rearing each nymph, or else by careful dis- 
section and examination of the developing genital structures in 
mature nymphs. 
Leuctra sibleyi Claassen 
(Plate 9, figs. 147-152.) 
Length of body up to 8 mm.; antennae up to 3.8 mm.; cerci 
up to 4 (?) mm. 
General color yellowish brown to darker brown. 
Head considerably wider than pronotum; rounded behind; 
hind ocelli at least twice as close to the eyes as to each other; 
front ocellus placed on a line in front of the anterior margin of 
the compound eyes; surface smooth; antennae about half as long 
as body, with about forty-eight segments. 
Pronotum only slightly wider than jong; sides nearly straight ; 
angles rounded, the posterior ones more so than the anterior 
ones; surface nearly smooth, slightly hairy, and with longer 
hairs on the outer margins at the angles; anterior marginal 
groove narrow and not prominent. Hind wing pads set closely 
together so that the inner margins are almost contiguous. Legs 
rather short, stocky and not much flattened; sparsely covered 
with short hairs, and only a very few longer hairs on the femora 
and tibiae; first tarsal segment more than twice as long as second ; 
third almost twice as long as one and two combined. 
Abdomen cylindrical, rather slender and -somewhat widened 
near the middle; sides of segments nearly straight; surface 
covered with short stout hairs, and the posterior margin with a 
series of short spinules; tenth tergite broadly rounded in both 
male and female nymphs. In the male there appears a small 
lobe-like protuberance just below the tenth abdominal tergite ; 
within this protuberance, the supra-anal process may be seen in 
mature nymphs. Cerci rather stout and at least half as long as 
the body; the basal segments slightly wider than long; near the 
middle they are about three times as long as wide, and at the tip at 
least six times as long as wide; there are about eighteen or twenty 
segments in each cercus, each segment with a whorl of long hairs 
near the apex. 
Mouth parts. Labrum at least half again as wide as long; an- 
terior margin slightly concave in the middle and fringed with 
