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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.

Dorsal view of a Zapada cinctipes (Nemouridae) (Tiny Winter Black) Stonefly Nymph from the Yakima River in Washington
Nymphs of this species were fairly common in late-winter kick net samples from the upper Yakima River. Although I could not find a key to species of Zapada nymphs, a revision of the Nemouridae family by Baumann (1975) includes the following helpful sentence: "2 cervical gills on each side of midline, 1 arising inside and 1 outside of lateral cervical sclerites, usually single and elongate, sometimes constricted but with 3 or 4 branches arising beyond gill base in Zapada cinctipes." This specimen clearly has the branches and is within the range of that species.
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 Ephemerella excrucians (Pale Morning Dun) Mayfly Dun Pictures

This "specimen" is actually two different duns, one missing the middle front and back left legs, the other missing the terminal filament i.e. middle tail. I added them together by accident, but since they're the same species, stage, and gender, I might as well leave them together.

Ruler view of a Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho The smallest ruler marks are 1 mm.
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Lateral view of a Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Dorsal view of a Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Ventral view of a Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho
Ruler view of a Female Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Big Lost River in Idaho The smallest ruler marks are 1 mm.

This mayfly was collected from the Big Lost River in Idaho on August 2nd, 2020 and added to Troutnut.com by Troutnut on August 18th, 2020.


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Female Ephemerella excrucians (Pale Morning Dun) Mayfly Dun Pictures

Collection details
Location: Big Lost River, Idaho
Date: August 2nd, 2020
Added to site: August 18th, 2020
Author: Troutnut
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