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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.

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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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Female Sweltsa (Sallfly) Stonefly Adult Pictures

These stoneflies--abundant during midday--seemed at first to be flying around with plain yellow bodies, but on closer inspection turn out to have striking, fiery red abdomens.

Lateral view of a Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana
Ruler view of a Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana The smallest ruler marks are 1 mm.
Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana
Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana
Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana
Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana
Ventral view of a Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana
Artistic view of a Female Sweltsa (Chloroperlidae) (Sallfly) Stonefly Adult from the Madison River in Montana

This stonefly was collected from the Madison River in Montana on June 30th, 2019 and added to Troutnut.com by Troutnut on July 17th, 2019.

Discussions of this Adult

Sweltsa?
1 replies
Posted by Taxon on Jul 17, 2019
Last reply on Jul 17, 2019 by Troutnut
Hi Jason-

My guess would be genus Sweltsa, of which I believe there to be ~8 species in MT. It looks pretty similar to a (mostly) dorsal view of Sweltsa townsesi, which is pictured in American Stoneflies: A Photographic Guide to the Plecoptera by Bill B. Stark, et. al. However, I believe that species is only present in the Northern Sierra Nevada Mountains of CA and NV.
Anyone able to ID this Chloroperlid?
Posted by Troutnut on Jul 17, 2019
Last reply on Jul 17, 2019 by Troutnut
I didn't do the best job taking pictures of key characteristics (such as wing venation), but I'm hoping somebody might be familiar with the striking color pattern. I'd love to know the species on this one.

Start a Discussion of Adult

References

Female Sweltsa (Sallfly) Stonefly Adult Pictures

Collection details
Location: Madison River, Montana
Date: June 30th, 2019
Added to site: July 17th, 2019
Author: Troutnut
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