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Salmonflies
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Stonefly Species Calineuria californica (Golden Stone)

Calineuria californica is the largest western species of the Perlidae family, with female adults approaching 40 mm in some locales. This species is perhaps better known by anglers under its former scientific name, Acroneuria californica. It is the primary Golden Stonefly hatch of the West Coast states, a role shared by Hesperoperla pacifica to a lesser degree. Their roles are reversed in the Rocky Mountain states where pacifica takes the top billing. Both are now commonly known as Golden Stones as regional colloquial differences have slowly dissipated. They were both commonly called Brown Willowflies in the Rockies and Golden Stones in the coastal states, which explains the confusion caused by references in older fly fishing literature.

This large stonefly is ubiquitous in western freestones and can provide incredible angling at ther height of their activity. On rivers lacking populations of Pteronarcys californica, they are the largest and most significant hatch of the year. They are generally a late spring/early summer emerger. They crawl out of the water to perch on streamside riparian foliage or rocks where they shed their nymphal shucks. They also mate in the same locations. The females end up back on the water in good numbers and offer good dry fly fishing. But it is the nymphs that offer the best angling opportunities, especially as they stage in the shallows in preparation for emergence.

The nymphs lack anal gills which easily separates them from Hesperoperla and Claassenia. Their lateral ocelli (simple eyes) in a pale background separates them from Doroneuria.

The male adults of Calineuria and Hesperoperla are easy to tell apart by looking at their hammers. Both are quadrangular but Calineuria is longer than wide. The heads and pronotums of both sexes are dramatically marked in Calineuria while Hesperoperla is more plain.

Where & when

Time of year : Late Spring, early Summer

Specimens of the Stonefly Species Calineuria californica

2 Female Adults
1 Male Adult
Male Calineuria californica (Golden Stone) Stonefly Adult
A few of these larger stoneflies were fluttering around the South Fork on an evening dominated by much smaller species.

This one has been difficult to identify. I can't spot any of the gill remnants characteristic of Perlidae, but the wing venation seems to point in that direction. I tried keying it out as Perlodidae but arrived at Isoperla, every western species of which has significantly smaller bodies than this one.

Edit: See forum comments for a likely correct identification.
3 Nymphs

1 Streamside Picture of Calineuria californica Stoneflies:

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References

Taxonomy
Species Range
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