PLECOPTERA NYMPHS OF NORTH AMERICA 48 
that they live in swift water, are carnivorous, and probably have 
a two-year life cycle. 
Key to the Nymphs of Perlodes 
1. Small finger-like gills present only on the outer base of the 
submentum; no gills on thorax........ americana (p. 44) 
Small finger-like gills on the sides of the thorax in addition 
Pet UOR GLI ON LUessUDMENTUM, 41a vena dba cus anne etree hae es 2 
2. Four pairs of finger-like gills; one pair on submentum, three 
Dains.on the sides. of the thorax. 4.5. .3.- signata (p. 43) 
Three pairs of finger-like gills; one pair on submentum and 
ey Oa OREO GORE kien co yen sot once reek eee tibialis (p. 44) 
Perlodes signata Hagen 
(Plate 12, figs. 181-182.) 
Length of body up to 28 mm.; antennae up to 10 mm.; cerci 
up to 10 mm. 
General color yellowish brown, varied with yellow markings; 
the brown accentuated by the presence of an irregular coating 
of short brown hairs. 
Head about as wide as long, thick, with very large maxillae 
which protrude each side so as to be visible from above; three 
small ocelli arranged in a triangle whose base is greater than its 
sides; yellow frontal M-line distinct; a yellow mark each side 
of the ocellar triangle; the occipital ridge meets the epicranial 
suture at the vertex, thus forming a triangular field on the inside 
of each eye, these triangles each containing a large rounded area 
of reticulate yellow markings; labrum and lateral portions of 
clypeus brown; antennae of some fifty-five segments. 
Pronotum narrower than head, broader than long; front mar- 
gin nearly straight; sides a little convex; hind margin convex 
but with the narrow marginal groove concave in center; all angles 
rounded ; median line yellow; lateral field with yellow markings; 
meso- and metanotum similarly marked; wing pads almost paral- 
lel with body. Legs yellowish brown; thick fringes of long white 
hairs on the outer margins of the femora and tibiae; first and 
second tarsal segments very short, subequal. 
Four pairs of single small, finger-like gills located as follows: 
one pair at the outer base of the submentum; second pair at the 
outer anterior base of the prothoracic legs; third pair on the 
lateral margin of the conjunctivae between the pro- and meso- 
