Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York

Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Stream photos

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Perlodidae (Springflies and Yellow Stones) Stonefly Nymph Perlodidae (Springflies and Yellow Stones) Stonefly Nymph

Artistic view of a Perlodidae (Springflies and Yellow Stones) Stonefly Nymph from the Yakima River in Washington

This one seems to lead to Couplet 35 of the Key to Genera of Perlodidae Nymphs and the genus Isoperla, but I'm skeptical that's correct based on the general look. I need to get it under the microscope to review several choices in the key, and it'll probably end up a different Perlodidae.

11 Recently Added Photos

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 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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