ee 
May, 
Fig. 386.—Epeorus namatus, mature nymph, 
dorsal aspect. 
low this, a bank of pectinate spines. In the 
legs, the femora are relatively long and 
slender, with a closely set row of bristles 
along the posterior margin of each; each 
tarsal claw is short, rather slender at the 
base, and has two to six extremely minute, 
ventral denticles near the tip. Gills are 
borne by abdominal segments 1-7; each gill, 
fig. 327, is composed of a ventral, platelike 
element and a much-reduced, dorsal tuft of 
filaments; the anterior and posterior pairs 
of gills may or may not project beneath the 
abdominal venter to form, with the inter- 
mediate gills, a partial or complete, ventral, 
adhesive disc. There are only two long 
caudal filaments; the median one is atro- 
phied. 
Burks: THE MaAyrties oF ILLINOIS 195 
The nymphs of Epeorus inhabit shallow, 
cool or cold, rapidly flowing water. 
The genus Epeorus is well represented in 
the western and northeastern states, but is 
extremely rare in the Midwest. Epeorus 
namatus (Burks) (1946:607), figs. 386, 
387, was described from Indiana and vitrea 
(Walker) (1853:555) is known from Mani- 
toba, Michigan, New York, Ontario, Penn- 
sylvania, and Quebec. Either or both of 
these might eventually be collected in IIli- 
nois. 
44. CINYGMULA McDunnough 
Cinygmula McDunnough (19335:75). 
In the adult males of Cinygmula, the 
compound eyes are large, but are not quite 
contiguous on the meson; each fore leg is 
about as long as the body, with the femur 
three-fourths as long as the tibia and the 
tarsus one and one-fourth to one and one- 
half times as long as the tibia; the first tar- 
sal segment is from three-fifths to three- 
fourths as long as the second segment. The 
wing venation in both sexes is typical for 
the family, with the stigmatic crossveins of 
the fore wing not at all, or only slightly, 
anastomosed; the wing membrane often is 
suffused with a gray or yellow tint. Vein 
M, in the hind wing diverges from M, in 
the center of the wing. In the male genitalia, 
the forceps have four segments, the second 
of which is the longest and is about as long 
as the third and fourth segments combined; 
the penis lobes, fig. 388, are rather long and 
slender, have conspicuous lateral and mesal 
spines, and are either entirely separate or 
fused on the meson at the base only. The 
terminal abdominal sternite of the female 
has a V-shaped, median indentation on the 
posterior margin. 
In the nymphs, the frontal margin of the 
head is emarginate on the meson, exposing 
a small portion of the labrum when viewed 
in dorsal aspect. The femora are relatively 
long, narrow, and flattened, and the tarsal 
claws are short, stout, and bear only three to 
five minute, ventral denticles. A pair of gills 
is present on each of abdominal segments 
1-7; these gills are similar on all segments, 
each being platelike, with the fibrillar portion 
either entirely wanting or reduced to two 
or three filaments, fig. 328; the gills nor- 
mally are held against the sides of the abdo- 
men and project over the tergites but do not 
