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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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Female Attenella margarita (Little Western Blue-Winged Olive) Mayfly Dun Pictures

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.

Lateral view of a Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York
Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York
Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York
Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York
Ventral view of a Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York
Ruler view of a Female Attenella margarita (Ephemerellidae) (Little Western Blue-Winged Olive) Mayfly Dun from Willowemoc Creek in New York The smallest ruler marks are 1 mm.

This mayfly was collected from Willowemoc Creek in New York on September 4th, 2006 and added to Troutnut.com by Troutnut on October 3rd, 2006.

Discussions of this Dun

ID on this little olive?
3 replies
Posted by Troutnut on Oct 3, 2006
Last reply on Oct 4, 2006 by GONZO
My Ephemerellidae keys are pretty much garbage when it comes to identifying female duns. I'm wondering if anybody has any insight on this one based on personal experience.

There can't be all that many tiny olive Ephemerellids hatching in September. My tentative guess would be Serratella.

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Female Attenella margarita (Little Western Blue-Winged Olive) Mayfly Dun Pictures

Collection details
Location: Willowemoc Creek, New York
Date: September 4th, 2006
Added to site: October 3rd, 2006
Author: Troutnut
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