May, 1953 
low- or red-brown; sternites light yellow or 
tan, each sternite usually with an arcuate, 
transverse row of four black dots. Geni- 
talia, fig. 143, bright yellow, penis lobes 
vase shaped, greatly enlarged at bases, 
second forceps segment slightly enlarged at 
apex; caudal filaments yellow to almost 
white, articulations light reddish brown. 
NympH.—Length of body 8-10 mm., of 
caudal filaments 5—7 mm. Body dark brown, 
flecked with tan dots; abdomen often with 
a longitudinal, dorsal tan stripe; caudal fila- 
ments usually with alternating, broad cross- 
bands of brown and tan. 
Head with well-developed occipital tu- 
bercles, fig. 153; maxillary palps wanting. 
Thorax lacking dorsal tubercles; each tarsal 
claw bearing 9 to 12 denticles. Postero- 
lateral angles of abdominal segments 2-9 
produced, spinelike, those borne by segments 
2 and 3 minute, fig. 164; abdominal tergites 
1-4 each with a pair of finger-like, sub- 
median tubercles, tergites 5—7 each with a 
pair of narrow, acute, submedian spines, and 
segments 8 and 9 each with a pair of rudi- 
mentary spines, these spines and tubercles 
forming two parallel rows; platelike gills 
borne by abdominal segment 4 not entirely 
covering more posterior gills; caudal fila- 
ments bearing long, dense setae in apical 
areas. 
Known from Georgia, Illinois, Michigan, 
New Brunswick, New York, North Caro- 
lina, Ontario, Quebec, and Wisconsin. De- 
velops in rather small, shallow lakes. 
Illinois Records.—Freeport: at light, 
June 11, 1948, Burks, Stannard, Smith, 3 @. 
GRAYSLAKE: May 26, 1936, H. H. Ross, 
IN. Havana, Illinois River: May 21, 1895, 
C. A. Hart, 1 N; shore of Cook’s Island, 
May 17, 1894, C. A. Hart, 1 N; Quiver 
Lake, June 1-2, 1894, Smith, 1 N; outlet 
Quiver Lake, June 1, 1895, C. A. Hart, 
1 N. Lake County: Cedar Lake, June 
19, 1892, Hart & Shiga, 8 N; Fourth Lake, 
June 16-20, 1892, Hart & Shiga, 14 N; 
Sand Lake, June 15, 1892, Hart & Shiga, 
2 N. Wicuert: June 9, 1948, Burks, Stan- 
nard, & Smith, 1¢. 
25. Ephemerella coxalis McDunnough 
Ephemerella coxalis McDunnough 
(1926: 186; 1931a:37). 
Mare.—Length of body and of fore wing 
7-8 mm. Thorax and abdomen brown, with 
Burks: THE Mayr ties or ILirois UE 
large, yellow markings; venter light yellow; 
wings and wing veins hyaline. Genitalia, 
fig. 144, quite similar to those of lutulenta, 
with minor differences in details of structure 
of peritreme opening. 
NympH.—Head with small occipital tu- 
bercles. Thorax without dorsal tubercles; 
each tarsal claw with six to nine denticles. 
Abdominal tergites 1-7 bearing two rows of 
relatively large, submedian tubercles, fig. 
159, these two rows diverging posteriorly, 
caudal filaments with long setae in apical 
regions. 
Known from Georgia, Indiana, North 
Carolina, Ontario, and Quebec. 
26. Ephemerella simplex McDunnough 
? Ephemerella unicornis Needham (1905: 45). 
Ephemerella simplex McDunnough 
(1925¢:41; 1931d: 208). 
Mave.—Length of body and of fore wing 
6-7 mm. Head dark brown to black, base 
of each antennal scape surrounded by a 
yellowish ring; antennae dark brown; eyes 
deep red-brown. Thoracic dorsum dark 
brown to black, with minute, light red-brown 
markings at sutures; thoracic venter vaguely 
marked with light brown; fore leg black, 
fading to gray-yellow toward apex of tarsus; 
middle and hind legs yellow, coxae brown, 
apexes of tibiae and tarsal segments shaded 
with faint brown; all wings hyaline, veins 
stained with brown, those near costal margin 
of fore wing darker. Abdominal tergites 
very dark brown, apical tergites vaguely 
marked with yellow-brown spots; sternum 
chiefly dark yellow-brown, slightly lighter 
on sternites 7 and 8; sternite 9 dark brown 
to black; genitalia, fig. 146, dark smoky 
brown; caudal filaments uniformly gray- 
tan, articulations not darker. 
FEMALE—Length of body 5-7 mm., of 
fore wing 7-8 mm. In general, same color as 
male, but with vertex of head and areas of 
thoracic pleura at wing bases stained with 
deep yellow or red and thoracic venter with 
large, dark yellow areas; all legs dusky 
yellow, with coxae mostly dark brown; 
wings hyaline, veins near costal margin of 
each fore wing stained faintly yellow, other 
veins hyaline; caudal filaments very light 
yellow, with basal articulations red-brown. 
NympH.—Length of body 6-8 mm., of 
caudal filaments 4-6 mm. Body and appen- 
dages extremely broad, flat, and_ hairy. 
