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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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Mayfly Species Rhithrogena futilis (Western Gordon Quills)

This uncommon and slightly larger species hatches earlier than Rhithrogena hageni, but otherwise is virtually indistinguishable.

Where & when

Time of year : Late May through July

The best populations of Rhithrogena futilis are in the upper Northwest, but they are found elsewhere in the Rockies.

In 4 records from GBIF, adults of this species have been collected during July (50%) and August (50%).

Species Range

Hatching behavior

Time of day : Morning

Spinner behavior

Swisher and Richards mention in Selective Trout that the duns of this species are not important but the spinners can be.

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

Body length: 11 mm
Wing length: 11.5 mm

Scarcely distinguishable except on genital characters from Rhithrogena doddsi (now a synonym of Rhithrogena hageni). As compared with the type series of this latter species, the present one is slightly larger in size and the general color is a deeper brown. The abdomen is very narrowly ringed with light ochreous in the interspaceal area and on dorsum this pale area shows a faint smoky transverse streak. Anterior to the base of forewing is a light ochreous patch tinged with ruddy-brown posteriorly and bisected by a blackish streak. The usual dark streaks are present on the femora. As compared with those of doddsi the male genitalia show narrower and slightly more divergent penis-lobes apically, the centro-ventral small spine is lacking and in its place we find a small dorsal spine in much the same position; the minute apical spines on outer edge of each lobe which are present in most of the species of the group are somewhat better developed than in doddsi, but not as strong as in Rhithrogena morrisoni.


Start a Discussion of Rhithrogena futilis

References

Mayfly Species Rhithrogena futilis (Western Gordon Quills)

Taxonomy
Species Range
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