PLECOPTERA NYMPHS OF NORTH AMERICA 97 
Head wider than pronotum; broadly rounded behind; rather 
smooth; three ocelli, the posterior ones about twice as close to the 
eyes as to each other. 
Pronotum about as wide as or slightly wider than long; sides 
nearly straight; angles rounded; surface somewhat hairy, espe- 
cially around the outer margin; anterior marginal groove in- 
distinct. Legs rather stocky and only sparsely clothed with long 
hairs; first segment of tarsus at least twice as long as second; 
sometimes the second is indistinct; third much longer than one 
and two combined. 
Abdomen eylindrie, covered with short hairs, and with a fringe 
of short hairs on the posterior margin of each segment. 
Gills absent. 
The sexes are not so readily recognizable as in some other 
genera. The males are smaller and a little more slender than the 
females. In the males may be noticed a small protuberance in 
which the supra-anal process develops. 
The mouth parts are of the herbivorous type and indicate that 
all the species in the genus are vegetable feeders. The labium is 
different in structure from the labia in related genera, in that 
the glossae are only about half as wide as the paraglossae, and 
the labial palpus extends much beyond the paraglossae. In gen- 
eral, the structure of the mouth parts is so similar in the different 
species within a genus that the description and figures of the 
mouth parts of L. sibley2 may well be said to describe the general 
structure of the mouth parts of the entire genus. 
The nymphs are commonly found in small upland streams 
where they occur in leaf drifts and other forms of vegetable mat- 
ter. Because of théir inconspicuous brown color and small size, 
and their habit of clinging to brown leaves and sticks, the nymphs 
are not readily observed, and are therefore quite scarce in col- 
lections. 
Although we have no records of any life-history studies within 
the genus, they probably require one year to complete the life 
eycle. The adults of most species emerge in the summer, although 
some are found emerging as early as March and others as late 
as November. 
I have been able to identify with certainty the nymphs of only 
two species, LZ. decepta and LD. sibleyr. Judging from the close 
similarity in the shape, size, color, and structure of the nymphs 
of these two species to the many other nymphs in the collection 
from various localities, it appears that specific identification in 
this genus will be very difficult. No reliable characters have yet 
