150 Intinois NarurAL History Survey BULLETIN 
June 17, 1947, L. J. Stannard, 22. Dixon: 
at light, June 26, 1947, B. D. Burks, 1°. 
KeirHssurc: at light on Mississippi River, 
June, 1932, 14. Mount Carme-: at light, 
Burks & Sanderson, 12. PROPHETSTOWN: 
dredging sandy bottom of Rock River 15 
yards from bank, May 21, 1925, R. E. Rich- 
ardson, 1 N; sweeping vegetation on bank of 
Rock River, June 26, 1947, B. D. Burks, 
14, 22. Quincy: at light, June 8, 1939, 
Burks & Riegel, 12 ; July 6, 1939, Mohr & 
Riegel, 12. Rock FAtts: at light, June 26, 
1947, B. D. Burks, 12. Rockrorp: June 2, 
1944, H. S. Dybas, 1°. 
40. SIPHLOPLECTON Clemens 
Siphloplecton Clemens (1915a:258). 
The adult wing venation in Siphloplecton 
is very similar to that in the heptageniid 
type, differing principally in that the cubital 
intercalary veins of the fore wing are partly 
or completely joined by crossveins to the 
branches of Cu, fig. 308. In the true hepta- 
geniid wing, these intercalary veins are free 
at the bases, as in fig. 317. In the hind wing 
of Siphloplecton, vein M is forked near the 
base, fig. 308. The hind tarsus has four 
clearly differentiated segments. The abdo- 
men is relatively long and slender, and the 
ninth sternite of the female is entire and 
not greatly produced posteriorly, fig. 306. 
There are two long caudal filaments, with 
the median one represented by a three- to 
six-segmented stub. 
In the nymphs, which are streamlined 
and fishlike, the eyes are placed laterally on 
the head, which is typically baetid in form, 
as in fig. 305. The mouth-parts are evi- 
dently not fitted for predatism. Each fore 
tarsal claw is bifid, fig. 303; all other claws 
are slender and longer than the tibiae, fig. 
302. Gills are present on abdominal seg- 
ments 1-7; these gills are single and plate- 
like on segments 4-7 and double on seg- 
ments 1-3, except in interlineatum, where 
the gills of segments 1-3 have merely a 
small, recurved ventral flap. There are three 
well-developed caudal filaments; each of the 
cerci has long, dense setae on the mesal side 
only. 
This genus includes four species, only 
one of which has been taken in Illinois. 
Another species occurs in Indiana and it will 
probably eventually be found to occur in 
Illinois. 
Vol. 26, Art. 1 
KEY TO SPECIES 
ADULTS 
Crossveins in entire fore wing brown, hind wing 
with entire basal third shaded with brown. . 
iT os oP bal oe 1. basale 
Crossveins in fore wing brown only near costal 
margin and along stem of R45; hind wing 
with brown shading confined to area around 
bases of C, Sc, and R...2. interlineatum 
Mature Nympus 
Median ventral stripe of abdomen continuous, 
uninterrupted; claw of middle leg 10 times 
as long as wide at base.......... 1. basale 
Median ventral stripe of abdomen interrupted 
at each intersegmental suture; claw of middle 
leg 7 to 8 times as long as wide at base..... 
See ey ee: 2. interlineatum 
1. Siphloplecton basale (Walker) 
Baetis basalis Walker (1853:565). 
Siphlurus flexus Clemens (1913:338). 
Mave.—Thorax dark brown, with white 
areas on pleura. Each fore wing with a 
prominent, brown color pattern in anterior 
basal area; hind wing with an intense, brown 
cloud at base, fig. 308. Abdominal dorsum 
dark brown; sternum white, with ster- 
nites 1 and 9 dark brown and intermediate 
sternites each with three brown dots, one 
median and two lateral; genitalia as shown 
in fig. 311. 
FEMALE.—Similar to the male but color 
lighter in tone, with brown shading at wing 
bases faint or absent. 
Ny™mMPH.—Three longitudinal, brown 
bands present on abdominal venter; gills on 
segments 1-3 double; each caudal filament 
with a dark, broad, vaguely defined cross- 
band located just distad of middle. 
Known from Indiana, Manitoba, Michi- 
gan, New York, North Carolina, Ontario, 
and Quebec. 
2. Siphloplecton interlineatum (Walsh) 
Baetis femorata Walsh (1862:386), not Say. 
Misidentification. 
Baetis interlineata Walsh (1863:190). 
New name. 
Mate.—Length of body and of fore wing 
12-14 mm. Head and thorax dark brown 
to black, with light yellow markings on 
pleura and sternum. Wings hyaline, small 
area of brown staining at each wing base, 
costal crossveins margined with brown; 
short, longitudinal, brown dash in second 
interspace below bulla; fore leg gray-tan, 
