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.

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.

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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 Eurylophella temporalis (Chocolate Dun) Mayfly Spinner Pictures

This male spinner molted from a dun I photographed a few days earlier, as did a female of the same species that I captured with it.
It keys confidently to Eurylophella temporalis using Allen & Edmunds (1963), primarily based on the shape of the penes, which is more distinctive for this species than for most others in the genus. However, the remainder of the description of the male spinner in that paper fits this specimen perfectly as well.

Lateral view of a Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

Dorsal view of a Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

Ruler view of a Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin The smallest ruler marks are 1 mm.

Ventral view of a Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

The weird fibers obscuring the view aren't a part of the insect here, obviously.

Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

Full terminalia of the male spinner

Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

Lateral view of penes, ventral side down

Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

Dorsal view of the penes. The apparent projections on the side are just unrelated debris.

Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

Ventral view of the penes detached from the claspers.

Male Eurylophella temporalis (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the West Fork of the Chippewa River in Wisconsin

This mayfly was collected from the West Fork of the Chippewa River in Wisconsin on June 21st, 2021 and added to Troutnut.com by Troutnut on June 24th, 2021.

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References

Allen, R.K., and Edmunds, George F. Jr. 1963. A Revision of the Genus Ephemerella (Ephemeroptera: Ephemerellidae) VII. The Subgenus Eurylophella. Canadian Entomologist 95: 597-623.