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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

Dorsal view of a Grammotaulius betteni (Limnephilidae) (Northern Caddisfly) Caddisfly Larva from the Yakima River in Washington
This is a striking caddis larva with an interesting color pattern on the head. Here are some characteristics I was able to see under the microscope, but could not easily expose for a picture:
- The prosternal horn is present.
- The mandible is clearly toothed, not formed into a uniform scraper blade.
- The seems to be only 2 major setae on the ventral edge of the hind femur.
- Chloride epithelia seem to be absent from the dorsal side of any abdominal segments.
Based on these characteristics and the ones more easily visible from the pictures, this seems to be Grammotaulius. The key's description of the case is spot-on: "Case cylindrical, made of longitudinally arranged sedge or similar leaves," as is the description of the markings on the head, "Dorsum of head light brownish yellow with numerous discrete, small, dark spots." The spot pattern on the head is a very good match to figure 19.312 of Merritt R.W., Cummins, K.W., and Berg, M.B. (2019). The species ID is based on Grammotaulius betteni being the only species of this genus known in Washington state.
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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Female Hesperoperla pacifica (Golden Stone) Stonefly Adult Pictures

I collected this specimen as a nymph and had it in line to be photographed, but it emerged inside my holding container before I got the chance. However, I was able to get some interesting photos of the very freshly-emerged adult that really demonstrate how strikingly colors can change within a few short hours after emergence. The before-and-after pictures are combined here under a single specimen since they portray the same individual at different times within the same stage.

Based on the identification of another specimen from the same date/site, I'm calling this Hesperoperla pacifica.

Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Lateral view of a Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Ruler view of a Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana The smallest ruler marks are 1 mm.
Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana
Ventral view of a Female Hesperoperla pacifica (Perlidae) (Golden Stone) Stonefly Adult from the Gallatin River in Montana

This stonefly was collected from the Gallatin River in Montana on July 2nd, 2019 and added to Troutnut.com by Troutnut on July 18th, 2019.


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Female Hesperoperla pacifica (Golden Stone) Stonefly Adult Pictures

Collection details
Location: Gallatin River, Montana
Date: July 2nd, 2019
Added to site: July 18th, 2019
Author: Troutnut
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