May, 1953 
& Burks, 2 N; June 3-4, 1947, B. D. Burks, 
eal 9. 
12. Ephemerella aurivillii (Bengtsson) 
Chitonophora aurivillii Bengtsson 
(1908 :243; 1909:8). 
Ephemerella aronti Eaton (1908: 149). 
Ephemerella norda McDunnough (1924d: 223). 
Chitonophora aurivilliusi Lestage 
(1930a: 204). Emended name. 
Ephemerella concinnata Traver (1934:219). 
New synonymy. 
Mave.—Length of body 10-11 mm., of 
fore wing 11-12 mm. Thorax red-brown, 
with lateral areas dark brown; wings hya- 
line, with stigmatic areas milky and veins 
brown. Abdominal tergites with anterior 
third of each segment light brown and pos- 
terior two-thirds dark brown; abdominal 
sternites yellow-brown; caudal filaments 
uniformly dark brown. Genitalia, fig. 130, 
distinct from those of all other North Amer- 
ican species: penis lobes divided almost to 
bases, inner margins of lobes provided with 
numerous minute spines; second forceps seg- 
ment suddenly enlarged at apex. 
NympH.—Head and thorax entirely lack- 
ing dorsal spines or tubercles; maxillary 
palps well developed; each fore femur bear- 
ing spicules at posterior margin and near 
dorsal apex; each tarsal claw with 8 to 11 
denticles; each abdominal tergite with a 
pair of light-colored, submesal spots at pos- 
terior margin, on each spot a cluster of 
minute spines and a small, acute tubercle; 
caudal filaments with long setae near apexes. 
Known from Alaska, Alberta, Labrador, 
Michigan, Montana, Ontario, Pennsylvania, 
Quebec, and northern Europe. This species 
is distributed throughout the northern part 
of the Holarctic region. 
13. Ephemerella septentrionalis 
McDunnough 
Ephemerella septentrionalis McDunnough 
(1925b:171; 1931d:201). 
Mate.—Length of body 8-9 mm., of fore 
wing 10-11 mm. Dorsum of thorax and 
abdomen brown; venter yellow-brown; 
wings and wing veins hyaline. Genitalia, 
fig. 134, distinct from those of all other 
eastern North American species: slender 
lateral projections of penis lobe are virtually 
straight and directed posteriorly; mesal area 
Burks: THE Mayrties oF ILLINOIS 69 
of each lobe with two or three stout spines; 
second forceps segment relatively straight, 
but enlarged suddenly at apex. 
NympH.—Head, thorax, and abdomen 
without dorsal spines or tubercles; legs 
conspicuously long, slender, and hairy; each 
tarsal claw with 10 to 12 denticles; caudal 
filaments bearing long setae in apical regions. 
Known from New York, Ontario, and 
Quebec. 
14. Ephemerella argo Burks 
Ephemerella argo Burks (1949: 232). 
Mate.—Length of body 8 mm., of fore 
wing 9 mm. Thorax light yellowish tan, 
with vague brown markings; abdomen light 
yellowish tan, tergites with large areas 
shaded with brown. 
Head deep cream colored, vertex with ob- 
scure, light gray markings; each antennal 
scape and pedicel cream colored, flagellum 
brown; eyes yellowish tan. Legs deep cream 
colored, apex of fore tibia and second and 
third fore tarsal segments darkened; wings 
hyaline, stigmatic areas milky, anterior veins 
slightly yellow stained, other veins hyaline. 
Abdominal tergites light yellowish tan, with 
brown shading: mid-dorsal area of tergites 
1-4 almost completely brown, tergites 5 and 
6 shaded only near meson, tergites 7-10 
completely brown, shaded on mid-dorsal 
area; venter of abdomen light yellowish, 
with vague, longitudinal, brown line near 
each lateral margin of each sternite; geni- 
talia, fig. 138, light yellowish tan; caudal 
filaments light yellowish tan, articulations 
brown. 
NympH.—Length of body 7-9 mm., of 
caudal filaments +5 mm. Body principally 
yellowish tan, with a prominent, brown color 
pattern, fig. 173; caudal filaments each with 
one to three narrow, brown crossbands in 
middle and apical areas. 
Head, thorax, and abdomen without dor- 
sal spines or tubercles; maxillary palps well 
developed; each tarsal claw with six to nine 
denticles; posterolateral angles of abdominal 
segments 3-9 produced, spinelike; caudal 
filaments bearing long setae in apical areas. 
Known from Illinois and Indiana. Prob- 
ably a large-river species. 
Illinois Record.—Mount CarMe_Et, Wa- 
bash River: April 2, 1932, Frison & Ross, 
ZANS 
