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.

Waterfalls over smooth bedrock above Titcomb Lakes

From Titcomb Basin in Wyoming

Stream photos

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Setvena wahkeena (Wahkeena Springfly) Stonefly Nymph Setvena wahkeena (Wahkeena Springfly) Stonefly Nymph

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.

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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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Mayfly Species Isonychia intermedia (Slate Drakes)

Species Range

source

Map of specific collection sites

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.

Male Spinner

Described in Needham et al (1935)

Body length: 12 mm
Wing length: 12 mm

A dark purplish red species, having pale antero-lateral triangles on the abdominal segments; venation dark brown.

Thoracic notum intense raw-umber brown, somewhat paler before the scutellum of the mesonotum. Fore leg about 2/3 as long as the body. Femur and tibia dark brown, femur rather paler at base; tarsus light brownish red, the first joint yellowish. Middle and hind legs light yellow, the claws and tarsal joinings narrowly purplish brown. Wings hyaline, venation dark brown; large longitudinal veins paler toward the wing base.

Abdomen intense purplish red. Tergites with yellowish white triangles occupying the antero-lateral angles, and between these and the median line another pale streak at the anterior margin. These spots increase in size posteriorly. Smaller pale triangles occupy the antero-lateral angles of the sternites. Sternite 10 and the forceps dull yellowish brown, washed with reddish purple; forceps base purplish red. Apical margin of the forceps base deeply excavated as in Isonychia sicca.

Start a Discussion of Isonychia intermedia

References

Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.