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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Case view of a Pycnopsyche guttifera (Limnephilidae) (Great Autumn Brown Sedge) Caddisfly Larva from the Yakima River in Washington
It's only barely visible in one of my pictures, but I confirmed under the microscope that this one has a prosternal horn and the antennae are mid-way between the eyes and front of the head capsule.

I'm calling this one Pycnopsyche, but it's a bit perplexing. It seems to key definitively to at least Couplet 8 of the Key to Genera of Limnephilidae Larvae. That narrows it down to three genera, and the case seems wrong for the other two. The case looks right for Pycnopsyche, and it fits one of the key characteristics: "Abdominal sternum II without chloride epithelium and abdominal segment IX with only single seta on each side of dorsal sclerite." However, the characteristic "metanotal sa1 sclerites not fused, although often contiguous" does not seem to fit well. Those sclerites sure look fused to me, although I can make out a thin groove in the touching halves in the anterior half under the microscope. Perhaps this is a regional variation.

The only species of Pycnopsyche documented in Washington state is Pycnopsyche guttifera, and the colors and markings around the head of this specimen seem to match very well a specimen of that species from Massachusetts on Bugguide. So I am placing it in that species for now.

Whatever species this is, I photographed another specimen of seemingly the same species from the same spot a couple months later.
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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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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