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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 Holocentropus (Polycentropodidae) Caddisfly Larva from the Yakima River in Washington
This one seems to tentatively key to Holocentropus, although I can't make out the anal spines in Couplet 7 of the Key to Genera of Polycentropodidae Larvae nor the dark bands in Couplet 4 of the Key to Genera of Polycentropodidae Larvae, making me wonder if I went wrong somewhere in keying it out. I don't see where that could have happened, though. It might also be that it's a very immature larva and doesn't possess all the identifying characteristics in the key yet. If Holocentropus is correct, then Holocentropus flavus and Holocentropus interruptus are the two likely possibilities based on range, but I was not able to find a description of their larvae.
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 oregonensis (Brown Duns)

Where & when

In 1 records from GBIF, adults of this species have been collected during April (100%).

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: 10 mm
Wing length: 11 mm

Both wings of this species are suffused with brown at the base; genitalia are quite distinctive.

Head and thorax blackish; pleura shaded with paler ruddy tinges. Fore legs deep blackish brown. Middle and hind legs light yellowish brown, the femora largely suffused with reddish brown. Wings hyaline, the costal area faintly amber-tinged at the base. The basal anal region of the fore wing is suffused with sepia brown, the stigmatic region similarly tinged. The whole basal area of the hind wing, extending along the costa half way to the apex, is prominently brown. Longitudinal and cross veins brown; cross veins numerous, those of the stigma anastomosed. Second abdominal tergite suffused with smoky brown; tergites 8-6 semi-hyaline, pale yellowish white; posterior margins, triangles in the postero-lateral corners, and two narrow submedian streaks, dark brown, which in certain lights appears reddish. Tergites 7-9 opaque, similarly marked, but the dark areas blackish brown. Tergite 10 largely brown, the posterior margin pale. Sternites 1-6 semi-hyaline, pale yellowish white; 7-9 opaque, suffused somewhat with brown. Forceps base pale, forceps deep smoky. Penes unique, each composed of a rather wide chitinous piece bearing at its apex three broad spines; penes short, not reaching to the apex of the forceps base (see fig. 117). Tails pale smoky, not darkened at the joinings.

Specimens of the Mayfly Species Ameletus oregonensis

1 Male Spinner
1 Female Spinner

Discussions of Ameletus oregonensis

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Mayfly Species Ameletus oregonensis (Brown Duns)

Species Range
Common Name
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