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with, occasionally, faint tan crossbands; 
wings hyaline, with veins faintly yellow. 
Genitalia, fig. 145, differ from those of in- 
varia in possessing a ventral, subbasal group 
of two or three spines on each penis lobe. 
NympH.—Dorsal tubercles on thorax and 
head absent, but dorsal, submedian abdom- 
inal spines present, although small, fig. 166; 
each tarsal claw with five to eight denticles; 
caudal filaments with long setae in apical 
regions. 
Known from Michigan, New York, North 
Carolina, Ontario, Quebec, and Wisconsin. 
BICOLOR Group 
22. Ephemerella prudentalis 
McDunnough 
Ephemerella prudentalis McDunnough 
(19314: 40). 
Mave.—Length of body and of fore wing 
7-8 mm. Thorax and basal abdominal ter- 
gites red-brown, color gradually changing 
to yellow on apical tergites; sternites yellow, 
with black markings; wings hyaline, brown 
stain at bases; veins hyaline, occasionally 
tinged with tan. Genitalia, figs. 140, 141, 
differ from those of all other eastern North 
American species in having a large, ventral, 
subapical enlargement on each penis lobe. 
NympH.—Head with a pair of small 
occipital tubercles; dorsum of abdominal 
tergites with two rows of submedian spines 
converging posteriorly; caudal filaments 
bearing long setae in apical areas. 
Known from Quebec. 
23. Ephemerella lutulenta Clemens 
Ephemerella lutulenta Clemens (1913: 335). 
Ephemerella lineata Clemens (1913:336). 
Mace.—Length of body 8-9 mm., of fore 
wing 9-10 mm. Thorax dark brown, ab- 
domen yellow-brown, peppered with minute, 
black dots. 
Head yellow-brown, with gray streaks on 
frons around ocelli and on frontal carina; 
antennae yellow-brown. Pleura and venter 
of thorax sprinkled with minute, black dots; 
wings hyaline, often faintly stained with 
brown at bases; veins brown; legs yellow- 
brown, partly or completely covered by a 
sprinkling of black dots. Both dorsum and 
venter of abdomen sprinkled with black dots; 
genitalia, fig. 139, yellow-brown, penis lobes 
with lateral margins straight and inner peri- 
Ittinois NarurAL History SurvEY BULLETIN 
Vol. 26, Art. 1 
treme angles blunt; second forceps segment 
slightly bowed toward apex; caudal filaments 
light yellow-brown near bases, becoming 
white at apexes, articulations dark brown. 
FEMALE.—Length of body and of fore 
wing same as in male; thorax and abdomen 
lighter colored than in male, causing sprin- 
kling of black dots to show more clearly; 
brown on wing veins lighter than in male. 
NympH.—Length of body 9-12 mm., of 
caudal filaments 6-8 mm. Uniformly dark 
yellow-brown, sometimes with small, vague, 
brown markings on dorsum of thorax; 
caudal filaments usually uniformly tan, 
sometimes with faint, brown crossbands. 
Occipital tubercles of female minute, those 
of male obsolete, as in figs. 151, 152; max- 
illary palps completely absent, as in fig. 169; 
each tarsal claw with 8 to 10 denticles. 
Posterolateral angles of abdominal segments 
2-9 produced as slender spines, those on 
segment 2 minute, those on segments 3-8 
long and slightly curved inward at apexes; 
tergites 1-7 each with a pair of long, sub- 
median tubercles, fig. 158, these forming 
two rows diverging posteriorly; platelike 
gill of segment 4 operculate, almost or quite 
covering three posterior pairs of gills; caudal 
filaments with dense, long setae near apexes. 
Known from Illinois, Indiana, Maine, 
Massachusetts, New Brunswick, New York, 
North Carolina, Ontario, Quebec, Tennes- 
see, and Wisconsin. Develops in relatively 
small, shallow lakes. 
Illinois Records. — ANtTIocH, Channel 
Lake: May 16, 1936, Ross & Mohr, 1 N; 
May 27, 1936, H. H. Ross, 14; May 16, 
1938, B. D. Burks, 12, 1 N. 
24. Ephemerella temporalis McDunnough 
Ephemerella temporalis McDunnough 
(1924c:74; 1931a:35). 
Mavre.—Length of body 7-8 mm., of 
fore wing 8-10 mm. Thorax bright yellow- 
brown; abdominal dorsum mostly dark 
brown; sternum light yellow or tan. 
Head yellowish tan, eyes light reddish 
yellow; each antennal scape and pedicel 
yellowish tan, flagellum gray-brown. Wings 
hyaline, veins in costal region faintly stained 
with tan; legs bright yellow, apex of each 
fore femur and fore tibia shaded with tan. 
Abdominal tergites 2-7 dark brown, often 
with a vague, transverse, black mark at 
posterior margin of each, tergites 8-10 yel- 
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