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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.

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Larva from the Yakima River in Washington
With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Heptagenia pulla (Golden Dun) Mayfly Nymph Pictures

This specimen is interesting because Heptagenia pulla has not been reported from Washington or neighboring states (Saskatchewan is the closest), yet the distinctive key characteristics are clear. Furthermore, it might even be a species not listed on this site—Jacobus et al. (2014) writes, "the northern and western specimens of H. pulla may in fact be a synonym of the Palearctic species H. dalecarlica Bengtsson (Kjaerstad et al. 2012) and the true H. pulla may be restricted to eastern North America."

It keys to the genus Heptagenia because the tarsal claw has a single basal tooth, and the gills on segment 7 have fibrils.

For the species key in Jacobus et al. (2014):
1. The left mandible is planate, whereas the right mandible is angulate.
2. The labrum is much wider than long.
3. There's a thin light-colored streak lateral to the eye on the head.

Ruler view of a Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington The smallest ruler marks are 1 mm.
Dorsal view of a Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Ventral view of a Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington
Closeup of the mandibles with the labium removed, showing the asymmetry (straight edge on the insect's left side, angled on its right) that helps diagnose the species.

Heptagenia pulla (Heptageniidae) (Golden Dun) Mayfly Nymph from the Yakima River in Washington

This mayfly was collected from the Yakima River in Washington on April 9th, 2021 and added to Troutnut.com by Troutnut on April 12th, 2021.


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Heptagenia pulla (Golden Dun) Mayfly Nymph Pictures

Collection details
Location: Yakima River, Washington
Date: April 9th, 2021
Added to site: April 12th, 2021
Author: Troutnut
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