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Male Rhithrogena morrisoni (Western March Brown) Mayfly Spinner Pictures

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

Recent 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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