Mayfly Species Ameletus oregonensis (Brown Duns)

Both wings of this species are suffused with brown at the base; genitalia are quite distinctive.

Head and thorax blackish; pleura shaded with paler ruddy tinges. Fore legs deep blackish brown. Middle and hind legs light yellowish brown, the femora largely suffused with reddish brown. Wings hyaline, the costal area faintly amber-tinged at the base. The basal anal region of the fore wing is suffused with sepia brown, the stigmatic region similarly tinged. The whole basal area of the hind wing, extending along the costa half way to the apex, is prominently brown. Longitudinal and cross veins brown; cross veins numerous, those of the stigma anastomosed. Second abdominal tergite suffused with smoky brown; tergites 8-6 semi-hyaline, pale yellowish white; posterior margins, triangles in the postero-lateral corners, and two narrow submedian streaks, dark brown, which in certain lights appears reddish. Tergites 7-9 opaque, similarly marked, but the dark areas blackish brown. Tergite 10 largely brown, the posterior margin pale. Sternites 1-6 semi-hyaline, pale yellowish white; 7-9 opaque, suffused somewhat with brown. Forceps base pale, forceps deep smoky. Penes unique, each composed of a rather wide chitinous piece bearing at its apex three broad spines; penes short, not reaching to the apex of the forceps base (see fig. 117). Tails pale smoky, not darkened at the joinings.