Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana

Salmonflies
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Mount Deborah and Hess Mountains. Two of the greatest peaks of the Alaska Range rise behind the braided, glacial Susitna River. These massive mountains are 35 miles north of where I took this picture.

From the Susitna River in Alaska

Stream photos

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Male Baetidae (Blue-Winged Olive) Mayfly Dun Male Baetidae (Blue-Winged Olive) Mayfly Dun

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

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

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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

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?

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