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.

Stream photos

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Female Sweltsa borealis (Boreal Sallfly) Stonefly Adult Female Sweltsa borealis (Boreal Sallfly) Stonefly Adult

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.

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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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Stonefly Species Allocapnia sandersoni (Little Snowflies)

Species Range

source

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Description from GBIFthe Global Biodiversity Information Facility

Source: Epiproct And Dorsal Process Structure In The Allocapnia Forbesi Frison, Allocapnia Pygmaea (Burmeister), And Allocapnia Rickeri Frison Species Groups (Plecoptera: Capniidae), And Inclusion Of Allocapnia Minima (Newport) In A New Species Group

Male epiproct. Apical segment of upper limb ca. 286 µm long and armed on the apical ca. 202 µm with dense patch of wave-like spikes (Figs. 103 - 106); apical segment ca. 142 µm wide at base and slightly swollen to ca. 164 µm near base of armature; armed area gradually narrowed to a rounded tip. Basal segment of upper limb ca. 572 µm long and ca. 111 µm wide near mid-length; basal segment bears a shallow, longitudinal groove extending to near base of apical segment. Greatest width of lower limb ca. 198 µm; marginal area near spoon lined with sparse row of long setae. Male tergal process. Prominent raised, narrowly divided process on abdominal tergum 8 (Figs. 106 - 108). Process on tergum 8 ca. 214 µm wide and covered with scale-like structures; median notch of process ca. 36 µm wide.

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