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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 Clostoeca disjuncta (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington
This one was surprisingly straightforward to identify. The lack of a sclerite at the base of the lateral hump narrows the field quite a bit, and the other options followed fairly obvious characteristics to Clostoeca, which only has one species, Clostoeca disjuncta.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Male Rhithrogena morrisoni (Western March Brown) Mayfly Spinner Pictures

Lateral view of a Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Dorsal view of a Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Ventral view of a Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington
Ruler view of a Male Rhithrogena morrisoni (Heptageniidae) (Western March Brown) Mayfly Spinner from the South Fork Snoqualmie River in Washington The smallest ruler marks are 1/16".

This mayfly was collected from the South Fork Snoqualmie River in Washington on June 22nd, 2017 and added to Troutnut.com by Troutnut on June 23rd, 2017.

Discussions of this Spinner

Second opinions on this one's ID?
3 replies
Posted by Troutnut on Jun 23, 2017
Last reply on Jul 5, 2017 by Crepuscular
I tentatively keyed it out to Rhithrogena morrisoni based on Needham's Biology of Mayflies, but I'm not completely sure. Roger's website lists Rhithrogena emerging in Washington in March and April, and this one was collected June 22nd. But this did come from high up in a mountain stream after a year of very heavy snowpack, so it might be that far behind schedule. It also looks very much like the specimen Bob Newell posted from eastern Washington. What do Roger and others think?

Start a Discussion of Spinner

Male Rhithrogena morrisoni (Western March Brown) Mayfly Spinner Pictures

Collection details
Location: South Fork Snoqualmie River, Washington
Date: June 22nd, 2017
Added to site: June 23rd, 2017
Author: Troutnut
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