136 
1938, Ross & Burks, 14; Aug. 16, 1938, 
Ross & Burks, 4¢. Mount Carrotv: July 
14, 1944, Frison & Sanderson, 16. 
Munctre: June 8, 1927, Frison & Glasgow, 
14. Oakwoop: June 2, 1927, T. H. Frison, 
14; June 14, 1935, C. O. Mohr, 48, 12; 
July 4, 1946, Mohr & Burks, 1 6 ; Salt Fork 
River, June 23, 1948, B. D. Burks, 56. 
Orecon: July 4, 1946, Mohr & Burks, 3 4 ; 
July 9, 1925, T. H. Frison, 1¢, 19. Rock 
Crry: May 24, 1938, Ross & Burks, 14 ; 
May 30, 1938, Mohr & Burks, 24, 19. 
Sr. CHARLES: Fox River, July 8, 1948, Ross 
& Burks, 504. Sreriinc: at light, May 
22, 1941, Ross & Burks, 406. WHuLMING- 
TON: at light, Aug. 6, 1947, Burks & San- 
derson, 56. 
24. Baetis nanus McDunnough 
Baetis nanus McDunnough (1923:42). 
Mave.—Length of body 3 mm., of fore 
wing 4 mm. Head and thorax light gray- 
tan, with dorsal thoracic sutures shaded with 
brown; legs white, each fore femur yellow; 
hind wing with third longitudinal vein long, 
extending slightly beyond the middle of 
wing, and with a single marginal inter- 
calary vein usually present posterior to vein 
2; abdominal tergites 2-6 light yellow, apical 
tergites dark grayish yellow-brown; geni- 
talia and caudal filaments white. 
Known from Indiana and Ontario. 
25. Baetis phoebus McDunnough 
Baetis phoebus McDunnough (1923:41). 
Mave.—Length of body 5.0 mm., of fore 
wing 5.5 mm. Head and thorax brown, with 
yellow or yellow-brown shading on thoracic 
notum; legs faintly yellow, almost white; 
each fore wing with intercalary vein of first 
three interspaces of approximately equal 
length, fig. 288; hind wing with third longi- 
tudinal vein slightly more than one-half as 
long as wing, a single marginal intercalary 
vein present posterior to vein 2; abdominal 
tergites 2-6 white, apical tergites bright 
chestnut brown; genitalia and caudal fila- 
ments white. 
Known from Ontario. 
33. PSPEUDOCLOEON Klapalek 
Pseudocloeon Klapalek (1905:105). 
In this genus, the upper portion of each 
compound eye in the adult males is set on a 
Ittinois NarurAL History SurRvEY BULLETIN 
Vol. 26, Art. 1 
high stalk. In Illinois species, the height 
of this stalk is at least as great as the di- 
ameter of the lower portion of the eye. 
In some South American species of Pseudo- 
cloeon, the height of the stalk supporting 
the upper portion of the eye is several times 
as great as the diameter of the lower por- 
tion. Each compound eye in the females is 
small, and the two eyes are separated by a 
space at least three times as great as the 
width of one eye. In each fore wing, there 
are relatively few crossveins, the stigmatic 
area is usually milky, the stigmatic cross- 
veins are slanting and partly anastomosed, 
and the marginal intercalary veins occur in 
pairs. The hind wings are wanting. The 
male in all species known to me has a small, 
brown, or black, median dorsal dot on the 
base of the second abdominal segment; the 
basal 6 or 7 abdominal sternites in both 
sexes almost always show the blackened 
outlines of vestigial tracheae decurrent from 
the spiracles. In the male genitalia, the first 
forceps segment is about as broad as long, 
with the inner apical angle usually produced 
toward the meson, the second segment is 
narrower than the first, the third is long, 
slender, and usually bowed, and the fourth 
is small; there is a small penis cover be- 
tween the bases of the forceps. 
The nymphs are streamlined and typically 
live in the shallow, fairly rapidly flowing 
water along the banks of brooks or creeks. 
The maxillary palps have two segments, and 
the labial palps three. There is but a single 
pair of wingpads, the gills are single and 
platelike, and there usually are but two well- 
developed caudal filaments. The nymph of 
one species, minutum Daggy (1945:395), 
is described as having three well-developed 
caudal filaments. 
Pseudocloeon has 19 described Nearctic 
species, 5 of which occur in Illinois. Re- 
liable characteristics for the separation of 
the females of these species have not yet 
been found. 
KEY TO SPECIES 
Aputt MALEs 
1. Abdominal tergites 2-6 entirely white, or — 
white faintly tinged with tan, and with- 
out any markings except black spirac- — 
ular dots or lines. :<.. .. #2 see 2a 
Abdominal tergites 2-6 light tan or white, — 
with red, tan, or brown spots or dots. .3 — 
2. Abdominal sternites with midventral, — 
brown or black dots. .1. punctiventris — 
