May, 1953 
with a small, brown-stained area at base of 
each fore wing. Basal and apical abdominal 
tergites dark brown, with middle tergites 
brown at posterolateral areas only, the 
central and anterior areas white; anterior 
and posterior abdominal sternites tan, and 
middle sternites white; genitalia, fig. 213, 
tan; caudal filaments predominantly white. 
Known from the eastern states and south- 
eastern Canadian provinces. 
21. CHOROTERPES Eaton 
Choroterpes Eaton (1881: 194). 
The members of the genus Choroterpes 
are small, extremely delicate mayflies. The 
males have predominantly dark brown or 
black bodies, with the abdominal venter of 
each considerably lighter in color. The fe- 
males are rather uniformly light brown. 
The compound eyes of the males are semi- 
turbinate, as there is in each eye a very slight 
development of a stalk to set off the upper 
portion from the lower. The wings in both 
sexes are stained with brown or red-brown 
at the bases; otherwise, the wings are clear, 
with the crossveins and posterior longitudinal 
veins hyaline. The veins near the costal 
margin of each fore wing are faintly stained 
with brown. The posterior branch of the 
outer fork (vein R.) in the fore wing is not 
bent posteriorly near the base, fig. 190; vein 
M, diverges from M, near the center of 
the wing, but the basal part of M, is obso- 
lescent; there are four cubital intercalary 
veins, the anterior pair long and the pos- 
terior pair short. Each hind wing has a 
small costal angulation, vein Sc ends just 
distad of this angulation, and vein M is 
unbranched. 
In the male genitalia, fig. 214, there is a 
pair of long penis lobes which are fused on 
the meson only at the bases; these penis 
lobes lack appendages. Each arm of the 
forceps, arising from an undivided base, is 
four segmented, with the suture setting off 
the basal segment from the second segment 
extremely obscure. In the females, the 
terminal abdominal sternite is only slightly 
or not at all indented on the meson of the 
posterior margin. 
In the nymphs, the head and body are 
flattened dorsoventrally. The antennae are 
relatively short—only about as long as the 
head is wide. There are three segments in 
each of the labial and maxillary paips. The 
Burks: THE Mayrtigs oF ILLINOIS 95 
head itself is quadrate and strongly prog- 
nathous. Each tarsal claw is single, rela- 
tively short, thick at the base, and provided 
with a single row of ventral denticles near 
the tip. The first abdominal segment bears 
a pair of single, filamentous gills, fig. 195B; 
segments 2-7 have each a pair of bifid, 
lamelliform gills, each lamina having a 
spatulate terminal extension, figs. 1954, 
195C, which varies in shape among the 
different species. The median caudal fila- 
ment is longer than the cerci. 
Choroterpes basalis (Banks) 
Leptophiebia basalis Banks (1900: 248). 
Mate.—Head and thorax very dark 
brown; wing bases heavily stained with 
brown. Abdominal dorsum dark brown, 
variegated with white, and abdominal venter 
white; penis lobes, fig. 214, brown; genital 
forceps and caudal filaments white. 
Widely distributed throughout the east- 
ern states and southeastern Canada, it 
should be taken in Illinois eventually. 
22. HABROPHLEBIODES Ulmer 
Habrophlebiodes Ulmer (1920a: 39). 
The members of the genus Habrophle- 
biodes are small, extremely delicate, brown 
mayflies. In the males, the fore tarsus is as 
long as the fore tibia. The wings are clear 
or faintly stained with yellow; the longi- 
tudinal veins are well marked, but the cross- 
veins are all but invisible. The posterior 
branch of the outer fork (vein R.) in the 
fore wing is bent posteriorly near the base, 
fig. 191; vein M, is obsolete at the base, 
but apparently diverges from M, near the 
center of the wing; there are two cubital 
intercalary veins. Each hind wing has a 
finger-like costal projection, and vein Sc 
ends just distad of the projection. 
The male genital forceps arms arise from 
a deeply cleft base, fig. 215; the apical two 
segments are minute and_ subtriangular. 
The penis lobes are fused to the tips; each 
lobe bears a decurrent, lateral appendage. 
In the females, the well-developed ovipositor 
is formed by a prolongation of the seventh 
sternite and underlies the eighth. The ninth 
sternite is deeply cleft on the meson of the 
apical margin. The median caudal filament 
is longer than the cerci. 
The nymphs are very similar to those of 
