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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington
This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.
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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Ephemerella excrucians (Pale Morning Dun) Mayfly Nymph Pictures

Dorsal view of a Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
Lateral view of a Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
Ventral view of a Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
Ruler view of a Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington The smallest ruler marks are 1 mm.
Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
Fairly poor closeup photo of a tarsal claw

Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
Total lack of spines/tubercles on the abdominal segments

Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
This one's meant to show the setae on the edge of the adbominal segments

Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
I don't see any sign here of the excresences that would indicate Ephemerella tibialis

Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington
Maxilla closeup

Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Nymph from the Yakima River in Washington

This mayfly was collected from the Yakima River in Washington on April 9th, 2021 and added to Troutnut.com by Troutnut on April 12th, 2021.


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Ephemerella excrucians (Pale Morning Dun) Mayfly Nymph Pictures

Collection details
Location: Yakima River, Washington
Date: April 9th, 2021
Added to site: April 12th, 2021
Author: Troutnut
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