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

Blue-winged Olives
Baetis

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.

Stream photos

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Skwala (Large Springfly) Stonefly Nymph Skwala (Large Springfly) Stonefly Nymph

Dorsal view of a Skwala (Perlodidae) (Large Springfly) Stonefly Nymph from the Yakima River in Washington

This Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.

6 Recently Added Photos

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 Ameletus exquisitus (Brown Duns)

Where & when

In 2 records from GBIF, adults of this species have been collected during May (100%).

Species Range

source

Map of specific collection sites

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

Described in Needham et al (1935)

Body length: 14 mm
Wing length: 16 mm

A large clear-winged species; the stigmatic area tinged with dark brown, wings very faintly tinged throughout with brownish grey.

Mesonotum yellowish brown. Metanotum blackish brown. Fore leg blackish brown, knee yellowish brown. Middle and hind legs yellowish brown to brown, the femora with an apical band. Wings hyaline, tinged faintly with brownish grey throughout; stigmatic area of fore wing tinged with dark brown. Venation dark reddish brown.

Tergites rich yellowish brown; the posterior margins, the postero-lateral angles, and a submedian streak, darker brown. Tergite 10 without these dark marks. Segments 2-6 largely semi-translucent; apical segments opaque. Sternites 2-6 light brownish grey; 7-9 yellowish brown. Ganglionic marks brownish. Forceps base dark brown on the lateral margins. Forceps blackish brown. Tails dark brown, darker near the base; joinings darker.

Start a Discussion of Ameletus exquisitus

References

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