118 Ittrnois NATURAL History SuRVEY BULLETIN 
Vol. 26, Art. 1 
Fig. 266.—-Callibaetis ferrugineus, mature nymph, lateral aspect. 
and white on notum; legs tan, each femur 
with a subapical, dark brown ring. Abdom- 
inal dorsum usually mostly tan or white, 
with a median, dark brown spot at either 
lateral margin and a pair of large, sub- 
lateral, dark brown spots on each tergite 
2-7; median area of tergites 2 and 3 dark 
brown; tergites 8-9 mostly light brown; 
gills white, tracheae purple-brown, those on 
segments | and 2 triple, and on segments 
3-7 double; caudal filaments each with a 
dark brown, subapical crossband. 
Known from Illinois, lowa, Maine, Mary- 
land, Michigan, New York, and Wisconsin. 
Illinois Records.—Specimens, collected 
April 18 to September 23, are from Antioch, 
Channel Lake, East Dubuque, Elgin, Fox 
Lake, Freeport, Giant City State Park, 
Havana, Kickapoo State Park, Lake Bluff, 
McHenry, Richmond, Rockford, Rock Is- 
land, Rosecrans, Spring Grove, St. Charles, 
Waukegan, Wolf Lake, and Zion. 
3. Callibaetis brevicostatus Daggy 
Callibaetis brevicostatus Daggy (1945: 388). 
This species may prove to be a synonym 
of semicostatus Banks (1914:614), which 
was described from Manitoba. 
Mave.—Length of body and of fore wing 
8 mm. Fore wing stained with brown at 
bases of veins Rs to M, but otherwise hya- 
line; longitudinal veins brown, crossveins 
hyaline; costal crossveins weak but present, 
stagmatic crossveins slanted and partly anas- 
tomosed; fore wing with numerous cross- 
veins and paired marginal intercalary veins. 
Abdomen brown, and densely covered with 
dark brown, punctate dots; genitalia and 
caudal filaments white. 
Known from Minnesota and Saskatche- 
wan. 
4. Callibaetis skokianus Needham 
Callibaetis skokianus Needham (1903:215). 
This species might eventually prove to be 
a synonym of ferrugineus, as the two are 
separated principally on the color of the 
wings, a character that is known to vary 
in other species of the genus. Long series 
of specimens of both skokianus and ferru- 
gineus have, however, been studied and no 
intergrades between the two have as yet 
been found. 
Our recent collecting in Illinois has failed 
to produce the nymph of this species. The 
only specimens of the nymph of skokianus 
I have seen are those in the Cornell Uni- 
versity collection, and they are in very poor 
condition. 
Mate.—Length of body and of fore win 
9-10 mm. General color bright yellow- 
brown or tan, shaded with dark red-brown. 
Head yellow-brown, face tan below antennal 
sockets; each antennal scape yellow, brown 
at apex, pedicel usually entirely brown, 
flagellum yellow at base, shaded with brown 
in middle, white at apex; upper portion of 
each eye yellow, lower tan, with a brown 
band across middle. Thorax yellow or tan; 
a broad, median, longitudinal, dark brown — 
stripe present on mesonotum; pleura and 
sternum usually with brown, punctate dots; 
legs yellow or white, with apexes of all 
femora lightly shaded with tan, and each © 
fore tibia and tarsus entirely tan to brown; 
wings hyaline, three costal interspaces of 
each fore wing washed with tan or light — 
yellow-brown, stigmatic crossveins anasto- 
mosed, marginal intercalaries of outer wing 
margin usually double. Abdomen chestnut 
brown, with numerous dark brown, punctate 
dots, a dark brown, longitudinal, median 
band usually extending the length of the 
