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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
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.

Lateral view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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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Little Western Blue-Winged Olives

This common name refers to only one species. Click its scientific name to learn more.

Mayfly Species Attenella margarita

These are sometimes called Little Western Blue-Winged Olives.
Though having a national distribution, this species is considered by angling authorities to be important only in the West. In localized waters where it is abundant, it can be a significant hatch.
Lateral view of a Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York
I found this dun unusually late in the year for anything in the Ephemerellidae family in the East. It's also small for that family.
Dorsal view of a Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Nymph from the East Fork Big Lost River in Idaho
Notes from the microscope on the ID: Maxillary palp is present, distinctly 2-segmented, but very small. Gills on segment 4-7. This specimen has some unfortunate damage to the abdomen, but it's the only one I found in my sample.

Little Western Blue-Winged Olives

Scientific Name
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