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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Mayfly Species Anepeorus rusticus

Species Range

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Male Spinner

Body length: 8 mm
Wing length: 9 mm

A brownish species, thus distinct from the pale A. simplex (now a synonym of Spinadis simplex).

Head brown; eye margins opposite antennae tinged with ochreous. Thorax dull brown; pale ochreous tinges on pleura, especially anterior to wing roots. Fore legs brown, the tarsus rather blackish; middle and hind legs pale ochreous. Wings hyaline. Longitudinal veins pale, cross veins darker; the latter are very fine except in apical portion of fore wing, where they are thickened and “slightly anastomosed along costa” (McD.). Abdominal tergites dull clay-brown; basal segments somewhat semi-hyaline; tergites 8-10 light ochreous brown. Faint traces of submedian and lateral rows of small dark brown spots are present. Sternites somewhat paler than tergites; each sternite with "two small central dots and narrow lateral oblique dashes.” Forceps brownish ochreous; lateral apical portions of penes with fewer lobes than in A. simplex. Tails dirty whitish. Genitalia shown in fig. 112.

Start a Discussion of Anepeorus rusticus


  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Mayfly Species Anepeorus rusticus

Species Range
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