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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.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
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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