Mayfly Species Ameletus similior (Brown Duns)

A medium-sized species, distinguished by the dark heart-shaped ganglionic marks on venter of abdomen. Wings with faint clouds.

Head and thorax shiny blackish brown, in the male. Fore legs blackish brown; middle and hind legs lighter brown. Wings hyaline, veins dark, palest along the outer margin; some are faintly clouded with light umber brown, in the male.

Abdomen deep brown with lighter brown shading, the posterior margins definitely brown-ringed. Dark heart-shaped marks on ganglionic areas of sternites. Tubercles on the apical margin of the forceps base, between the forceps, rather poorly developed. Penes rather long and slender, only slightly incurved near the tip: each bears one or more spines on the inner margin (see fig. 117).

In the female, the thorax is rather bright reddish brown. Subanal plate of female rather small, covering less than half the tenth segment.