30 Intinois Natura History Survey BULLETIN 
Mesoscutum of thorax with three 
brown lines which 
Dorsal meson 
domen. 
longitudinal, 
converge toward scutellum. 
of metathorax vaguely stained with grayish 
obscure, 
Fig. 55.—Potamanthus sp., mature nymph, 
dorsal aspect. 
brown. All legs greatly reduced, semi- 
membranous, nonfunctional. 
Known from Alabama, Arkansas, Geor- 
gia, Illinois, Kansas, Manitoba, Missouri, 
Nebraska, Ontario, and Tennessee. De- 
velops in large, slow rivers. 
Illinois Records.—A.tTon : Aug. 29, 1913, 
22. Btoomincton: C. C. Adams, 109. 
CHAMPAIGN: Sept. 21, 1892, C. A. Hart, 
19. ExLizasetHTown: at light, July 14, 
Vol. 26, Art. 1 
1948, Mills & Ross, 12. Granpo Tower: 
Aug. 14, 1898, C. A. Hart, 732. Havana: 
Aug. 10, 1889, C. A. Hart, 1 9 ; White Oak 
Creek, Aug. 14, 1896, C. A. Hart, 39. 
Momence: Aug. 16, 1938, Ross & Burks, 
12. Oquawka: Sept. 26, 1947, H. H. 
Ross, 302. Quincy: Aug. 10, 1889, C. A. 
Hart, 12. SHAWNEETOWN: Oct. 3, 1942, 
Frison & Ross, 19. UrsBana: at light, 
Aug. 23, 1943, H. B. Petty, 592; Sept. 20, 
1909, 29. 
2. CAMPSURUS Eaton 
Campsurus Eaton (1868: 83). 
The adults of Campsurus differ from 
those of Tortopus mainly in the structure 
of the legs; the middle and hind legs in both 
sexes in Campsurus are completely aborted 
beyond the trochanters. The difference in 
the wing venation between the two, de- 
scribed by Needham & Murphy (1924: 23) 
when they defined the genus Tortopus, is 
not reliable, according to Ulmer (1942:108). 
Campsurus decoloratus (Hagen) (1861: 
43), known from Texas and Mexico, and 
circumfluus Ulmer (1942:110), described 
from Texas, are the only known Nearctic 
species. C. puella (Pictet) (1843: 145), 
described from Louisiana, has been tenta- 
tively placed in Campsurus, but is at present 
unidentifiable. 
POTAMANTHINAE 
The subfamily Potamanthinae corresponds 
to Ulmer’s family Potamanthidae (1933: 
199). It has only one Nearctic genus. 
3. POTAMANTHUS Pictet 
Potamanthus Pictet (1845: 208, pl. 25). 
The adults are fairly large, whitish may- 
flies with the vertex and the dorsum of the 
thorax light reddish brown. The marginal 
intercalary veins of the wings are not net- 
like, fig. 42. In the fore wing, the basal 
part of vein M, is more strongly curved 
to the rear than is vein Cu,, fig. 42, and the 
first anal vein is forked near the wing 
margin. In the hind wing, the costal pro- 
jection is acute and veins M, and M, 
diverge near the wing base. The middle 
and hind legs of the adults are functional. 
The male genitalia, fig. 61, have the penis 
lobes broad, flattened, and almost com- 
