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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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Male Baetidae (Blue-Winged Olive) Mayfly Dun Pictures

This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.

Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
Ventral view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
Dorsal view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
Lateral view of a Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This is the nymphal shuck from which this dun emerged.

Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington

This mayfly was collected from Mystery Creek #308 in Washington on April 23rd, 2023 and added to Troutnut.com by Troutnut on May 2nd, 2023.


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Male Baetidae (Blue-Winged Olive) Mayfly Dun Pictures

Collection details
Location: Mystery Creek #308, Washington
Date: April 23rd, 2023
Added to site: May 2nd, 2023
Author: Troutnut
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