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Stonefly Species Calineuria californica (Golden Stone)

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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 (
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Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
Here's an underwater view of the pupal shucks of several already-emerged Brachycentrus numerosus caddisflies.
Shuck: The shed exoskeleton left over when an insect molts into its next stage or instar. Most often it describes the last nymphal or pupal skin exited during emergence into a winged adult.). 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 (Lateral: To the side.) ocelli (
The ocelli of a male Isonychia bicolor mayfly spinner.
The ocelli of a male Isonychia bicolor mayfly spinner.
Ocellus: A simple non-compound, single lens eye found in many arthropods. Mayflies have three ocelli in between their compound eyes.) (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 (Hammer: A smooth clearly defined chitinous area on the ventral surface of the ninth abdominal segment of some male stoneflies used for drumming up mates.). 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


Region: West

Time Of Year (?): Late Spring, early Summer



Pictures of 4 Stonefly Specimens in the Species Calineuria californica:

Specimen Page:12
Female Calineuria californica (Golden Stone) Stonefly AdultFemale Calineuria californica (Golden Stone) Stonefly Adult View 17 PicturesI caught this female in the vegetation on a trail about 50 feet above the stream. The coloration on its head differs from that of a male I collected recently on a nearby river, and from another female I collected on the same river. But it still keys out confidently to Calineuria, and californica is the only species of that genus in the area.
Collected July 25, 2019 from Mystery Creek #249 in Washington
Added to Troutnut.com by Troutnut on July 26, 2019
Male Calineuria californica (Golden Stone) Stonefly AdultMale Calineuria californica (Golden Stone) Stonefly Adult View 15 PicturesA 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 (Venation: The pattern in which the veins on the wings of an insect are arranged. It is usually one of the most useful identifying characteristics.) 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.
Collected July 20, 2019 from the South Fork Snoqualmie River in Washington
Added to Troutnut.com by Troutnut on July 22, 2019
Female Calineuria californica (Golden Stone) Stonefly AdultFemale Calineuria californica (Golden Stone) Stonefly Adult View 1 Pictures
Collected June 17, 2011 from the Grande Rhonde River in Washington
Added to Troutnut.com by Bnewell on June 26, 2011
Specimen Page:12

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