198 Ittinois NaturAL History SurvEY BULLETIN 
FEMALE.—Size as in male. Color similar 
to that of male, but generally lighter, the 
dark brown of the male being replaced by 
lighter brown, and light yellow being re- 
placed by white. 
NympH.—Length of body 6.5-7.5 mm. 
Head, thoracic dorsum, and abdominal ter- 
Vol. 26, Art. 1 
Hittspace: Rock River, July 29, 1925, D. 
H. Thompson, 1 N. Lynpon: Rock River, 
July 8, 1925, D. H. Thompson, 28 N; July 
15, 1925, 5 N; Aug. 5, 1924, () ieee 
Mitrorp: Rock River, at mouth Kishwau- 
kee River, July 14, 1927, D. H. Thompson, 
5 N. Orecon: Rock River, below bridge, 
392 
Fig. 391.—Rhithrogena pellucida, male genitalia. 
Fig. 392.—Anepeorus simplex, male genitalia. (After McDunnough.) 
Fig. 393.—Arthroplea bipunctata, male genitalia. 
gites 1-7 and 10 dark chestnut brown, ter- 
gites 8 and 9 yellow except at lateral mar- 
gins. Thoracic sternum white, with narrow, 
brown lines at edges of sclerites; each femur 
light brown, variegated with white in middle 
and at either end, and with scattered, dark 
brown dots in basal two-thirds; tarsal claws 
brown at tips. Abdominal venter tan or 
yellowish, sternites 2-8 each with a brown, 
median patch and a dark brown, transverse 
line at the posterior margin, and a brown- 
shaded area near lateral margins; lamellate 
portion of each gill white, fibrillar portion 
faintly stained with tan; caudal filaments 
tan. 
This swift-water species is known from 
Illinois, Michigan, and Minnesota. 
Illinois Records.—Como: Elkhorn 
Creek, June 18, 1925, D. H. Thompson, 2 
N; Rock River, July 6, 1925, 2 N; Aug. 12, 
1924, 1 N. Dixon: Rock River, May 12, 
1925, D. H. Thompson, many exuviae; May 
22, 1925, 1 N. Erie: Rock River, July 23, 
1925, D. H. Thompson, 1 N. Granp De- 
TOUR: Rock River, May 27, 1927, 9 N. 
May 24, 1927, D. H. Thompson, 1 N; July 
11, 1929, T. H. Frison, 1 N. PortTLanp: 
Rock River, July 21, 1925, D. H. Thompson, 
1 N. Roscoz: Rock River, Aug. 20, 1925, 
D. H. Thompson, 7 N. Srertrne: Rock 
River, Aug. 7, 1924, D. H. Thompson, 1 N. 
47. ANEPEORUS McDunnough 
Anepeorus McDunnough (19255:190). 
In the males of Anepeorus, the compound 
eyes are only moderately large and are sep- 
arated on the meson by a space at least as 
great as the width of one eye; each fore leg 
is only slightly longer than the middle or 
hind leg; the fore tibia is one and one-third 
times as long as the fore femur, and the fore 
tarsus is only two-thirds as long as the fore 
tibia; the second tarsal segment is one and _ 
one-half times as long as the first, slightly — 
longer than the third, and one and one-half 
times as long as the fourth, the fifth segment 
being slightly shorter than the fourth seg- 
ment. In both sexes, the wing venation is 
typical for the family, with the stigmatic — 
