May, 1953 
eral angles of segments 2-9 produced as 
large spines, apical angles slightly sinuate; 
sternites 2-8 each with a pair of sublateral, 
brown spots, sternite 9 with a pair of sub- 
lateral, brown spots near basal margin and 
a pair of very large, brown spots at apical 
margin, basal and apical spots sometimes 
connected and apical spots occasionally fus- 
ing on meson; each caudal filament deep 
yellow at base, alternating pairs of segments 
dark and light in middle and apical areas. 
Known from Alabama, Arkansas, Geor- 
gia, Illinois, Indiana, Iowa, Kansas, Michi- 
gan, Minnesota, Missouri, New York, 
Ohio, Oklahoma, Ontario, Pennsylvania, 
Quebec, Texas, and Wisconsin. 
Illinois Records.—Adult specimens, col- 
lected April 4 to August 23, are from Alto 
Pass, Anna, Antioch, Apple River Canyon 
State Park, Chicago, Cora, Elizabethtown, 
Evanston, Fox Lake, Golconda, Havana, 
Herod, Jonesboro, Monticello, Muncie, 
Oakwood, Parker, Spring Grove, St. Joseph, 
Wilmington, and Wolf Lake. 
11. Stenonema femoratum (Say) 
Baetis femorata Say (1823:162). 
Stenonema femoratum femoratum (Say). 
Spieth (1947:98). 
Mave.—Length of body 8-11 mm., of fore 
wing 10-13 mm. Differs from tripunctatum 
only in the following particulars: compound 
eyes separated on meson by a space only 
two-thirds as wide as lateral ocellus; outer 
margin of hind wing shaded with light 
brown; in dark specimens, area between in- 
ner and outer parapsides of mesonotum 
lighter brown than rest of mesonotum; geni- 
talia, fig. 342, with penis lobes relatively 
more truncate laterally; in most specimens, 
alternating articulations of caudal filaments 
darker brown than others. 
NympH.—Length of body 9-12 mm. Very 
similar to nymph of tripunctatum, but differ- 
ing in having anterior margin of head 
slightly flattened on meson, rather than 
evenly rounded from side to side, median, 
white spot on anterior margin absent; ab- 
dominal sternum with sublateral, brown 
spots usually present on sternites 5— or 6- 
8 only, occasionally spots entirely wanting 
from these sternites; sternite 9 always with 
sublateral, longitudinal, brown stripe and 
pair of large, brown spots at posterior mar- 
gin. 
Burks: THE MAYFLiés OF ILLINOIS 169 
Known from Georgia, Illinois, Indiana, 
New York, Ohio, Ontario, Quebec, and 
South Carolina. 
Illinois Records. — Asutey: Little 
Muddy River, April 29, 1946, Mohr & 
Burks, 136. CARBONDALE: June 13, 1944, 
Frison & Sanderson, 1g. Dr1xon Sprincs: 
at light, April 3, 1946, Burks and Sander- 
son, 5¢. Eppyvirte: Lusk Creek, April 4, 
1946, Burks & Sanderson, 1 6 ; Lusk Creek, 
May 24, 1940, Ross & Riegel, 14; Lusk 
Creek, June 1, 1940, B. D. Burks, 2 2 ; Belle 
Smith Springs, June 7, 1946, Mohr & Burks, 
94; Belle Smith Springs, July 16, 1946, 
Mills & Ross, 1 8. Fox Lake: July 1, 1931, 
Frison, Betten, & Ross, 1¢. Giant City 
STATE ParK: Aug. 22, 1944, Sanderson & 
Leighton, 128. Gotconpa: May 30, 1928, 
T. H. Frison, 16. HeErop: May 2, 1946, 
Burks & Sanderson, 16; May 23, 1946, 
Ross & Mohr, 1¢ ; May 29, 1939, Burks & 
Riegel, 1 3 ; July 8, 1935, DeLong & Ross, 
1g. Momence: June 22, 1938, Ross & 
Burks, 1 6. Oakwoop: May 7, 1936, Ross 
& Mohr, 1 ¢. PirrsFievp: at light, Aug. 11, 
1948, Sanderson & Stannard, 1 ¢@. Quincy: 
June 24, 1948, L. J. Stannard, 26. Rupbe- 
MENT: Blackman Creek, May 14, 1946, 
Mohr & Burks, 26. WAUKEGAN: Aug. 15, 
1938, Ross & Burks, 12. 
BIPUNCTATUM Group 
12. Stenonema bipunctatum 
(McDunnough) 
Ecdyonurus bipunctatus McDunnough 
(1926:191). 
Mace.—Length of body 6-8 mm., of fore 
wing 8-10 mm. Face below antennal sockets 
white, vertex red- or orange-brown; eyes in 
life pearl-gray; each antenna light yellow, 
flagellum usually slightly darkened in basal 
half. Thoracic notum dull gray-tan or gray- 
brown, with apex of mesoscutellum white; 
semimembranous area of pleuron anterior 
to base of fore wing, and dorsal to spiracle, 
pink, balance of pleuron white except for 
brown-shaded spot dorsal to each middle 
coxa; thoracic sternum light yellow; fore 
leg light tan, with red-brown shading in 
middle and at apex of fore femur, and with 
black shading at apex of fore tibia and at 
apexes of tarsal segments; first tarsal seg- 
ment two-thirds as long as second segment; 
middle and hind legs light yellow, each 
