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

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

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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Troutnut's profile picture
Bellevue, WA

Posts: 2758
Troutnut on Jun 23, 2017June 23rd, 2017, 6:32 am EDT
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?
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Jul 4, 2017July 4th, 2017, 3:47 pm EDT
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.
Best regards,
Roger Rohrbeck
Troutnut's profile picture
Bellevue, WA

Posts: 2758
Troutnut on Jul 4, 2017July 4th, 2017, 7:07 pm EDT
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.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Crepuscular's profile picture
Boiling Springs, PA

Posts: 920
Crepuscular on Jul 5, 2017July 5th, 2017, 1:00 am EDT
Nice. I like seeing these west coast mayflies. Hopefully one day I'll se them in person! Thanks for posting.

Be well,

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