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.

A small spring creek in Wisconsin. A little brook trout stream tumbles over boulders

Stream photos

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Epeorus albertae (Pink Lady) Mayfly Nymph Epeorus albertae (Pink Lady) Mayfly Nymph

Dorsal view of a Epeorus albertae (Heptageniidae) (Pink Lady) Mayfly Nymph from the East Fork Issaquah Creek in Washington

This specimen keys to the Epeorus albertae group of species. Of the five species in that group, the two known in Washington state are Epeorus albertae and Epeorus dulciana. Of the two, albertae has been collected in vastly more locations in Washington than dulciana, suggesting it is far more common. On that basis alone I'm tentatively putting this nymph in albertae, with the large caveat that there's no real information to rule out dulciana.

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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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Female Baetis (Blue-Winged Olive) Mayfly Dun Pictures

I'm guessing this specimen is in the genus Acerpenna because of the very sharp costal process on her hind wing. I'm guessing pygmaea because it is the most common species.

Editor note: Not Acerpenna. This is most likely Baetis. See comments on this male specimen for rationale. Also compare with the female specimen associated with it.