52 Inuinoris NaruraAt History Survey BULLETIN 
3. Caenis amica Hagen 
Caenis amica Hagen (1861:55). 
Ma ce.—Length of body and of fore wing 
2.0 mm. Vertex of head completely covered 
by dark gray shading; mesonotum yellow- 
brown; fore femur extensively shaded with 
dark gray, middle and hind femora each 
with a black, subapical, dorsal spot; ab- 
dominal tergites lightly shaded with gray, 
and spiracular dots present on abdominal 
segments 1-7 or -8; genital forceps, fig. 105, 
short and relatively slender. 
Known from Maine, Maryland, Missouri, 
North Carolina, New York, and West 
Virginia. 
4. Caenis simulans McDunnough | 
Caenis simulans McDunnough (1931¢:263). 
This is by far the commonest Illinois 
species of Caenis. 
Ma ce.—Length of body and of fore wing 
3.5-4.0 mm. Head below antennae yellow, 
vertex completely covered with dark pur- 
plish-gray shading; antennae yellow. Pro- 
notum light yellow, with dark purple-gray 
shading at margins and on dorsal meson; 
each fore coxa shaded with grayish brown, 
fore femur gray, with a black apicodorsal 
spot, fore tibia and tarsus light gray; meso- 
and metanotum chestnut brown, darker 
brown shading present on median dorsal 
suture or mesoscutum, just dorsad of wing 
bases, and at posterior ends of outer parap- 
sides ; apex of mesoscutum shaded with gray; 
gray shading present near either lateral 
margin of metanotum; each pleuron chest- 
nut brown, with dark gray shading around 
coxal cavities and light gray shading over 
prealar bridge; middle and hind legs white, 
with a black streak on outer side of each 
trochanter, and on dorsal side of each 
femur at base and near apex. Abdomen 
white or faintly stained with yellow, ter- 
gites 1-6 heavily shaded with dark gray, 
tergites 7—9 with gray shading in basolateral 
areas; black stigmatic dots or spots usually 
present on abdominal segments 1-9, these 
markings sometimes obsolete on segments 
8 and 9; each sternite typically with a black 
spot near either lateral margin and another 
black spot on meson, in addition to a pair of 
minute, sublateral, black dots on each of 
sternites 1-7 and a pair of sublateral, black 
dots on each of sternites 8-10; genital 
forceps, fig. 106, long and slightly bowed. 
Vol. 26, Art. 1 
FEMALE.—Length of body and of fore 
wing 4.0-5.5 mm. Coloration almost identical 
with that of male except that fore femur 
is light yellow, without gray shading, but 
with apicodorsal spots preserved; fore tibia 
and tarsus light yellow rather than gray, 
and median, black spots of abdominal ster- 
nites wanting or only faintly indicated. 
Known from the northern states and 
Canada. Develops in nearly or quite stag- 
nant water; it evidently tolerates consider- 
able pollution. 
Illinois Records.—Specimens, collected 
May 3 to August 19, are from Antioch, 
Banner, Beach, Chester, Fox Lake, Gol- 
conda, Havana, Herod, Kankakee, Mo- 
mence, Oakwood, Palos Park, Prophets- 
town, Richmond, Rosecrans, Serena, Spring 
Grove, Sterling, Wadsworth, and Zion. 
5. Caenis anceps Traver 
Caenis anceps Traver (1935a: 645). 
Mave.—Length of body and of fore wing 
2 mm. Vertex of head mostly white, with 
anterior and posterior margins edged with 
gray-purple, and with gray-purple shading 
near lateral ocelli; mesonotum light red- 
brown; fore femur shaded with gray at 
apex, and fore tibia shaded with gray at 
base; middle and hind femora white, with 
a minute, black, dorsal dot near apex of 
each; abdomen entirely white, without mark- 
ings of any kind; genital forceps, fig. 107, 
short and straight. 
Known from Missouri and New York. 
6. Caenis ridens McDunnough 
Caenis ridens McDunnough (1931¢:256). 
Mace.—Length of body and of fore wing 
2 mm. Head white, vertex lightly shaded 
with gray-purple, this shading darker near 
lateral and anterior ocelli, median area of 
vertex relatively pale; antennae white. Pro- 
notum white, with minute, purplish gray- 
shaded area at each anterolateral angle; 
gray-purple shading present around each 
fore coxal cavity and on fore coxa; fore leg 
white, fore femur faintly shaded with gray 
at apex, fore tibia gray; meso- and metano- 
tum pale yellow, with light purplish brown 
shading on median, longitudinal line of meso- 
scutum and on apex of mesoscutellum; 
pleuron light yellow, with purplish brown 
shading around coxal cavities; all thoracic 
