186 
a pair of lunate, submesal marks on each 
tergite; posterior margins of tergites shaded 
with dark brown; sternites yellow, with a 
broad, light red, shaded area at posterior 
margin of each; genitalia, fig. 365, yellow, 
shaded with red at apexes; caudal filaments 
almost white, articulations brown. 
NympH.—Length of body 11-13 mm. 
Head dark brown, with a white area on 
either side between compound eye and lat- 
eral margin of head. Each tarsal claw with 
a large basal tooth, ventral denticles want- 
ing. Dorsum of abdomen mostly dark 
brown, with prominent, white markings: ter- 
gites 1 and 2 mostly white, tergites 4 and 8 
each with a large, quadrate, white spot on 
meson at posterior margin, other tergites 
each with a pair of submesal and a pair of 
posterolateral, round, white spots; gills rel- 
atively small and oval, with filamentous, 
ventral tufts well developed and present 
in all gills; caudal filaments alternately 
brown and white throughout. 
Known from Manitoba, New York, Ohio, 
and Ontario. 
FLAVESCENS Group 
4. Heptagenia marginalis Banks 
Heptagenia marginalis Banks (1910:198). 
Mate.—Length of body and of fore wing 
9-10 mm. Head tan, with black markings 
along margin of frontal shelf, just below 
each antennal base, at either side of median 
ocellus, on vertex just posterior to each 
lateral ocellus, and along posterior margin 
of head; compound eyes separated on meson 
by a space as wide as one lateral ocellus. 
Thorax cream colored, with narrow, black 
lines on pleura; legs light yellow, almost 
white, each femur with a prominent, dark 
brown ring at apex, fore tibia and fore tarsal 
segments shaded with brown at apex; first 
fore tarsal segment one-sixth as long as 
second; wings hyaline, with veins and cross- 
veins brown. Abdomen white, each tergite 
with a narrow, black band across posterior 
margin and a pair of oblique, sublateral, 
black marks; genitalia, fig. 366, white; cau- 
dal filaments very light gray, with articula- 
tions slightly darker. 
FEMALE.—Length of body 9-10 mm., of 
fore wing 10-11 mm. Color pattern very 
similar to that of male, as all black marks 
of male are apparent in female, ground color 
ILtinois NaruraAL History Survey BULLETIN 
Vol. 26, Art. 1 
of body entirely white; caudal filaments 
white. 
NympH.—Length of body 10-11 mm. 
Head light brown, with small, white spots. 
Each tarsal claw with basal tooth, but 
ventral denticles wanting. Dorsum of ab- 
domen light brown, with a narrow, black 
crossband at posterior margin and a pair of 
sublateral, black streaks on each tergite; 
tergite | mostly white, following tergites 
each with a pair of sublateral, round, white 
spots; tergite 8 with a large, median, white 
blotch; abdominal sternum white to cream 
colored; gills semiovate, with fibrillar 
ventral tuft well developed on all segments; 
mamma sta ee ge A SORES aah? 
ees See — — = : =: are > = 
(SSS SSS FS es 5 IF OES AIA III RP SIU 
— 
Fig. 384. — Heptagenia flavescens, mature 
nymph, dorsal aspect. 
