> 
and an abdominal color pattern made up 
of dark longitudinal stripes and blotches on 
a very pale yellowish background. In the 
males, the fore leg is almost as long as the 
body. The fore wing, fig. 46, has the cross- 
veins at and posterior to the bulla crowded 
together so as to form a path extending 
halfway across the wing. The median 
caudal filament in both sexes is as long as 
each cercus. The cerci and the median 
caudal filament are extremely long—each 
more than twice as long as the body. 
In the nymphs, the frontal process of the 
head has a conspicuous, sharply projecting 
angle at each lateral margin, fig. 50. The 
mandibular tusks are long, slender, and 
smooth, with a few small, toothlike rasps 
on the outer,side near the base. The apex 
of the labial palp is broad and truncate. 
KEY TO SPECIES 
ADULTS 
1. Abdomen creamy white, without dark 
Pat RINGSs k= 156 ee eins 1. guttulata 
Abdomen yellowish or tan, with longi- 
tudinal, dark brown markings....... 2 
Hind wing with small, dark clouds sur- 
rounding discal crossveins, making wing 
appear spotted; genitalia with penis 
lobes relatively broad, fig. 63........ 
Hoa 35, bt chpauteare peenn ake; eas 2. simulans 
Hind wing not spotted, discal crossveins 
not surrounded by dark clouds; geni- 
talia with penis lobes relatively narrow, 
RO Te chsh ao SER eras 3. varia 
tr 
Mature Nympus 
1. Abdomen without color markings on 
MERGE Fo. his ote orien 1. guttulata 
Abdomen with longitudinal color markings 
OUPVGNEEE kos ries See hee OE hanes 2 
to 
Hind wingpad with dark color pattern 
SMEMUREE ooo). oc as eee 2. simulans 
Hind wingpad without indication of color 
MIGTUCENC SG sar al Seite sis pee 3. varia 
1. Ephemera guttulata Pictet 
Ephemera guttulata Pictet (1843:135). 
The wings appear to be almost solid 
brown because of the dense, dark red-brown 
pigmentation around and between the cross- 
veins; abdomen uniformly pale cream, with- 
out a darker color pattern, contrasting 
markedly with the very dark wings; cerci 
and median caudal filament tan to brown, 
with articulations very dark brown. Dis- 
tinctive genitalia of male figured by Need- 
ham (1921, pl. 81, fig. 58) and others. 
36 Inuinors NaruraAt History Survey BULLETIN 
Vol. 26, Art. 1 
Known from New York, Pennsylvania, 
and Quebec. 
2. Ephemera simulans Walker 
Ephemera simulans Walker (1853: 536). 
Ephemera natata Walker (1853: 551). 
Ephemera decora Walsh (1862: 376). 
Mare.—Length of body 10-12 mm., of 
fore wing 11-13 mm. Thorax mostly dark 
red-brown, with relatively small, light tan 
areas on pro- and mesopleuron; each fore 
leg dark red-brown, middle and hind legs 
tan to yellow; fore wing and hind wing, figs. 
46, 47, each with dark brown spots in discal 
area. Abdomen yellow to tan, with dark 
red-brown markings: each tergite with a 
pair of lateral dark blotches; each of apical 
three tergites with a pair of submedian, 
longitudinal, lateral stripes; sternites with 
longitudinal, lateral stripes, and a pair of 
submedian, longitudinal spots on each ster- 
nite; penis lobes, fig. 63, relatively wide; 
caudal filaments dark yellow-brown, with 
articulations darkened. 
FEMALE.—Length of body 11-13 mm., 
of fore wing 12-14 mm. Color pattern same 
as in male, but dark areas and spots relative- 
ly less extensive; legs light tan or yellow, 
fore legs shaded with light red-brown; 
caudal filaments light yellow, with brown 
articulations. 
Known from the northeastern and central 
states and eastern Canada. ‘This is one of 
the commonest mayflies in the Chicago 
region. It emerges along the lake front in 
enormous numbers every summer. ‘The 
nymph is found near the shores of lakes 
having considerable wave action and in 
moderate-sized rivers and creeks. 
Illinois Records—Cepar LAKE: Oct. 21, 
1882, 3 nymphs. Curicaco: July 31, 1887, 
C, A. Hart, 33; 39; July, Tae 
July 8, 1937, Frison & Ross, 436, 189. 
EppyvitLte: Lusk Creek, May 16, 1947, 
B. D. Burks, 19. Evanston: July 17, 
1938, G. T. Riegel, 23 ; July 9, 1939, G. T. 
Riegel, 1 ¢ ; July 22, 1942, J. S. Ayars, 2¢. 
Homer: June 30, 1925, T. H. Frison, 14 ; 
June 10, 1926, T. H. Frison, 99 ; June 30, 
1927, Frison & Glasgow, 96, 1192 ; Oct. 3, 
1946, L. J. Stannard, 2 nymphs. KanKa- 
KEE: June 12, 1931, Frison & Mohr, 26, 
39; June 5, 1932, Frison & Mohr, 22; 
May 31, 1938, Burks & Mohr, 32, 19; 
