. Bulletin. Natural history; Natural history. May, 1953 Burks: The Mayflies of Illinois 195. Fig. 386.—Epeorus namatus, mature nymph, dorsal aspect. low this, a bank of pectinate spines. In the legs, the femora are relatively long and slender, with a closely set row of bristles along the posterior margin of each; each tarsal claw is short, rather slender at the base, and has two to six extremely minute, ventral denticles near the tip. Gills are borne by abdominal segments 1—7; each gill, fig. 327, is composed of a ventral, platelike element and a much-reduced, dorsal tuft of filaments; the ant
. Bulletin. Natural history; Natural history. May, 1953 Burks: The Mayflies of Illinois 195. Fig. 386.—Epeorus namatus, mature nymph, dorsal aspect. low this, a bank of pectinate spines. In the legs, the femora are relatively long and slender, with a closely set row of bristles along the posterior margin of each; each tarsal claw is short, rather slender at the base, and has two to six extremely minute, ventral denticles near the tip. Gills are borne by abdominal segments 1—7; each gill, fig. 327, is composed of a ventral, platelike element and a much-reduced, dorsal tuft of filaments; the anterior and posterior pairs of gills may or may not project beneath the abdominal venter to form, with the inter- mediate gills, a partial or complete, ventral, adhesive disc. There are only two long caudal filaments; the median one is atro- phied. The nymphs of Epeorus inhabit shallow, cool or cold, rapidly flowing water. The genus Epeorus is well represented in the western and northeastern states, but is extremely rare in the Midwest. Epeorus namatus (Burks) (1946:607), figs. 386, 387, was described from Indiana and vitrea (Walker) (1853:555) is known from Mani- toba, Michigan, New York, Ontario, Penn- sylvania, and Quebec. Either or both of these might eventually be collected in Illi- nois. 44. CINYGMULA McDunnough Cinygmiila McDunnough (1933)!':75). In the adult males of Cinygmula, the compound eyes are large, but are not quite contiguous on the meson; each fore leg is about as long as the body, with the femur three-fourths as long as the tibia and the tarsus one and one-fourth to one and one- half times as long as the tibia; the first tar- sal segment is from three-fifths to three- fourths as long as the second segment. The wing venation in both sexes is typical for the family, with the stigmatic crossveins of the fore wing not at all, or only slightly, anastomosed; the wing membrane often is suffused with a gray or yellow tint. Vein M^ in the hind wing diverges from M^
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