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

Featured on the forum

Re: Trico emergers
In the Mayfly Genus Tricorythodes by Bwoklink (Martinlf replied)

Re: Trico Tips
In the Mayfly Genus Tricorythodes by Martinlf

Re: UV spectrum and trout
In General Discussion by Martinlf

Re: closing the gender gap in flyfishing
In General Discussion by Konchu (Smallflyguy replied)

Re: Fishing Kupa River, Slovenia
In Fishing Reports by Slocum (Fish1 replied)

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.

Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Species Acerpenna akataleptos

Species Range

source

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) as Baetis akataleptos

Body length: 2.5 mm
Wing length: 3 mm

Abdominal tergites 2-6 of male dull brown; genitalia of the Baetis intercalaris type ; hind wing two-veined, costal projection prominent.

Turbinate eyes of male imago small, oval in shape, and dark reddish brown. Thorax blackish brown. Legs pale smoky, the tarsi whitish. Wings hyaline, venation pale; cross veins in the stigmatic area of the fore wing few in number, not well developed, and without granulations. No intercalaries in the first interspace. Hind wing long and narrow; only two veins, the third one entirely lacking; costal projection prominent.

Abdominal tergites 2-6 semi-translucent, dull brown, sternites similar; posterior segments opaque, brighter brown. Genitalia very similar to B. pygmaeus (now a synonym of Acerpenna pygmaea), but with a finely setose projecting penis-cover, which is not present in that species, between the bases of the forceps. Related also to B. harti (now a synonym of Acerpenna pygmaea). Distinguishable from these species by reason of the brown basal segments of the abdomen.

Start a Discussion of Acerpenna akataleptos

References

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