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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.

Lateral view of a Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington
I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing this one.
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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This topic is about the Mayfly Species Stenonema terminatum

I have found no information about this species in angling literature, but one mediocre evening on the West Branch of the Delaware I found them to be a substantial part of the mixed bag of cahills and other mayflies causing a half-hearted rise of trout.

Example specimens

Troutnut
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Troutnut on Jun 8, 2007June 8th, 2007, 11:53 am EDT
I just wrote up what I found on the page for this species. I was mildly surprised to see so many of a species I've never seen mentioned in an angling context -- at least a few dozen throughout the evening. They piqued my curiosity.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Konchu
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Indiana

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Konchu on Jun 9, 2007June 9th, 2007, 2:05 am EDT
What more do ya wanna know?
Troutnut
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Bellevue, WA

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Troutnut on Jun 9, 2007June 9th, 2007, 4:20 am EDT
Hatch timing, habitat preference, quirky behavior... anything relevant to fishing that might be associated with this species.
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Konchu
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Indiana

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Konchu on Jun 11, 2007June 11th, 2007, 2:39 pm EDT
Larvae found on debris, rocks and aquatic vegetation in medium to large streams. Coarse sand/gravel substrate.

Spinners and duns are out around June-July in the Northeast and for a longer period (May-Aug) in the central and southern parts of its range.

Most of this was gleaned from:
Bednarik AF, McCafferty WP. 1979. Biosystematic revision of the genus Stenonema (Ephemeroptera: Heptageniidae). Can. Bull. Fish. Aquat. Sci. 201: 73 pp.

PS. This species was classified in the genus Stenonema until relatively recently.

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