May, 1953 
antennae tan. Mesonotum brown, shaded 
with darker brown at apex of scutellum; 
thoracic pleura light brown; sternum tan, 
becoming white on metasternum. Each fore 
leg white, with faint brown shading at 
apexes of femur, tibia, and tarsal segments; 
middle and hind legs white, each with faint 
brown shading at apexes of tarsal segments; 
wings hyaline, veins C, Sc, and R, brown at 
bases, light yellow distad. Abdominal ter- 
gum chestnut brown, the sternum white; 
the genital forceps and the caudal filaments 
white. 
NympH.—Length of body 7-9 mm. 
Frontal tubercles of head projecting as a 
pair of rounded protuberances; each gena 
produced above base of mandible as a broad, 
somewhat rounded ledge, fig. 178; long, 
relatively stout, lateral spines present on 
mesonotal shield, fig. 181; dorsal mesonotal 
spines wanting; maximum width of mesono- 
tal shield, not including lateral spines, three- 
fourths to four-fifths as great as maximum 
length of shield. 
Known from Illinois, Indiana, Manitoba, 
and Minnesota. Develops in fairly rapid 
creeks and moderate-sized rivers. The 
early instar nymphs occur in the swift cur- 
rent, while the late instar nymphs migrate 
to the comparatively still eddies along the 
banks. 
Illinois Records.—Byron: Rock River, 
May 20, 1927, 1 N. Dixon: Rock River, 
May 22, 1925, D. H. Thompson, 6 N. East 
DuBvuQueE: Mississippi River, May 9, 1941, 
Mohr & Burks, 1 N. Gotconpa: Big Grand 
Pierre Creek, May 13, 1932, Frison & Ross, 
3 N. Havana: Spoon River, April 22, 1898, 
C. A. Hart, 1 N; White Oak Creek, June 8, 
1940, Ross, Riegel, & Burks, 4 N. KAnKa- 
KEE: Kankakee River, May 22, 1912, 1 N. 
Momence: Kankakee River, May 16, 1940, 
B. D. Burks, 2 N; May 21, 1940, Mohr & 
Burks, 2 N; June 1, 1940, B. D. Burks, 
1g,1N. Oaxwoon: Salt Fork River, April 
18, 1948, Burks & Stannard, 2 N. Orecon: 
Rock River, May 25, 1927, D. H. Thomp- 
son, 2 N. PrcatTonica: Pecatonica River, 
June 3, 1926, D. H. Thompson, 1 N; May 
31, 1927, D. H. Thompson, 2 N. PropuHets- 
TOWN: Rock River, May 4, 1940, B. D. 
Burks, 1 N. Quincy: May 17, 1940, Mohr 
& Burks, 1 N. Rock Istanp: Rock River, 
fpril 18, 1931, T. H. Frison, 1 N. Sr. 
JosepH: Salt Fork River, June 11, 1940, 
Thompson & Burks, 19 N. 
Burks: THe Mayr ies or [LLINnots 79 
5. Baetisca lacustris McDunnough 
Baetisca lacustris McDunnough (1932b: 214). 
Mavre.—Length of fore wing 8 mm. 
Wings entirely hyaline, with veins C, Sc, 
and R, of fore wing only very faintly tinged 
with yellow; thoracic notum chestnut brown; 
abdominal tergites red-brown; sternites 
white or very pale yellow; genital forceps 
pale yellow; caudal filaments white. 
NympH.—Frontal tubercles of head 
greatly reduced and genae with small, shelf- 
like projections, fig. 177; mesonotal shield 
with long and sharp lateral spines; dorsal 
mesonotal spines wanting. 
Known from Manitoba, Ohio, and On- 
tario. 
OLIGONEURIIDAE 
The inclusion here of this family is neces- 
sitated by the occurrence in Illinois and In- 
diana of a curious nymph, fig. 184, which is 
certainly referable to the Oligoneuriidae. A 
remarkable adult, also belonging to this 
family, but not congeneric with our nymph, 
has been taken in Saskatchewan and Utah. 
c 
Sc+R, 
Cu, 
183 
Cu, 
Fig. 182. — Lachlania saskatchewanensis, 
wings. (After Ide.) 
Fig. 183. — Oligoneuria anomala, wings. 
(After Eaton.) 
