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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 Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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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Stenonema modestum (Cream Cahill) Mayfly Nymph Pictures

I looked at this nymph closely under my crappy microscope. It has truncate as opposed to rounded gills, postero-lateral spines only on abdominal segments 7-9, and oblique crossbars through the center of each sterna, not on the posterior edge like on some of the other Maccaffertium species. As best I can tell from the keys this is either modestum or ithaca and from the distribution maps I've seen I'm guessing it's modestum.

This mayfly was collected from unknown in Wisconsin on March 10th, 2004 and added to Troutnut.com by Troutnut on January 19th, 2006.


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Stenonema modestum (Cream Cahill) Mayfly Nymph Pictures

Collection details
Location: unknown, Wisconsin
Date: March 10th, 2004
Added to site: January 19th, 2006
Author: Troutnut
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