Mayfly Species Ameletus vernalis (Brown Duns)

A large clear-winged species with faint mid-ventral ganglionic marks on the abdomen.

Head and thorax deep blackish brown, the sutures yellowish. Fore femur deep blackish brown, a faint yellowish tinge at the base and a yellow line along the upper edge; tibia and tarsus black. Femora of middle and hind legs marked like fore femur, but slightly paler; tibiae and tarsi light brown. Wings hyaline, the fore wings shaded with brown on the apex and with a slight brown tinge at the base of R₃, where there is a group of 6 cross veins. Veins and cross veins brown except 3 or 4 costal cross veins beyond the bulla, which are pale and indistinct. Stigmatic cross veins anastomosed to form a series of smaller costal cells with larger ones below.

Abdominal segments 2-6 translucent, dull greyish white; segments 7-10 opaque yellowish. A dorsal series of deep purple-brown subtriangular patches is present on the tergites, the bases on the posterior margins, and with apices almost attaining the anterior margin. A similar series of lateral patches are brown in color, thus leaving pale anterior triangles between the darker ones. Tergite 9 is almost entirely brown. Sternites 2-6 show faint traces of mid-ventral brown spots connected by a fine line. Sternites 7 and 8 have brown lateral patches based on the posterior margins. Sternite 9 largely brown, yellowish on the posterior margin. Forceps deep smoky brown. A long spine below the penes on the inner side (see fig. 115).

Venter of female largely tinged with purplish brown.