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Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana
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 Amphizoa (Amphizoidae) Beetle Larva from Sears Creek in Washington
This is the first of it's family I've seen, collected from a tiny, fishless stream in the Cascades. The three species of this genus all live in the Northwest and are predators that primarily eat stonefly nymphs Merritt R.W., Cummins, K.W., and Berg, M.B. (2019).
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 Ameletus vancouverensis (Brown Duns)

Where & when

In 2 records from GBIF, adults of this species have been collected during August (50%) and May (50%).

Species Range

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: 9 mm
Wing length: 10 mm

The wings of this species are tinged throughout with umber brown; penes with two very long median spines.

Head and thorax deep mahogany brown. Mesothoracic scutellum light yellowish brown; two lateral arms extend forward from this area, thus forming with it a yellowish U-shaped patch. Pleura shaded with paler brown. Fore legs deep smoky brown; middle and hind legs umber brown, the femora with indications of a ruddy apical band. Wings tinged strongly and throughout with umber brown; stigmatic area even deeper brown; cross veins of the stigma anastomosed; both longitudinal and cross veins are dark brown, the cross veins very numerous. First abdominal segment deep mahogany brown; tergites 2-7 semi-hyaline, shiny light yellowish brown, the posterior margins narrowly dark brown, and the posterior half of each tinged with diffuse brownish shade. Tergites 8-10 are opaque, deep mahogany brown, tinged anteriorly with yellowish brown. Sternites 2-8 light ochreous, with a wash of dull brown; sternite 9 is rather bright yellow-brown in the central area, its base and lateral areas dark brown. Forceps base yellowish brown in central area, the apical and lateral margins mahogany brown; penes brown-tinged. Two long sharp spines are present between the lateral portions of the penes (see fig. 118). Tails deep smoky, joinings darker.

Start a Discussion of Ameletus vancouverensis


Mayfly Species Ameletus vancouverensis (Brown Duns)

Species Range
Common Name
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