1. Troutnut Forum
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2. Specimen Discussion
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3. Second opinions on this one's ID?

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?

Hi Jason-

Based on the shape of its penes, I believe Rhitrogena morrisoni is most likely.  As to its emergence in late June, my WA Aquatic Insect Emergence Chart is in error, as it should show emergence of various Rhitrogena species from early-Feb through mid-October.  Please see page 194 of Western Mayfly Hatches by Rick Hafele and Dave Hughes.

Thanks Roger. I checked with Bob Newell via email, to, and he concurred on the ID.

I suppose I should order a copy of Western Mayfly Hatches now that I live in the regular West.

Nice. I like seeing these west coast mayflies. Hopefully one day I'll se them in person! Thanks for posting.


Be well,
Eric