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Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana
Salmonflies
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Lateral view of a Psychodidae True Fly Larva from Mystery Creek #308 in Washington
This wild-looking little thing completely puzzled me. At first I was thinking beetle or month larva, until I got a look at the pictures on the computer screen. I made a couple of incorrect guesses before entomologist Greg Courtney pointed me in the right direction with Psychodidae. He suggested a possible genus of Thornburghiella, but could not rule out some other members of the tribe Pericomini.
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.

Ameletus cooki (Brown Dun) Mayfly Nymph Pictures

I caught this Ameletus nymph with several others of the same kind. This was the most vivid example, but they all had quite a bit of striking and unusual red shading, especially on the last few abdominal segments.

I keyed it out under the microscope using Larvae and adults of Ameletus mayflies (Ephemeroptera: Ameletidae) from Alberta with slightly larger (10 mm), mature specimen with darkened wingpads. Microscope pictures are from that specimen. The characteristics in the key and most of the verification table point pretty clearly to Ameletus cooki, except that the coloration of the antennae more closely resembles Ameletus sparsatus. However, on other characteristics in which these species differ (spines on the dorsal surface of the front femora, which seem very short in this specimen; length of posterolateral spines on segments 8–9; length of spines on posterior edge of tergites 6–9), this is a better match for cooki, and that's probably the correct ID.

Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Dorsal view of a Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ventral view of a Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ruler view of a Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington The smallest ruler marks are 1 mm.
Gill on abdominal segment 5

Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Gill on segment 5, closeup, removed and laid flat

Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ventral view, posterior margins of sternites 7-8

Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Posterolateral spines on segments 8–9

Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington
Dorsal view

Ameletus cooki (Ameletidae) (Brown Dun) Mayfly Nymph from the South Fork Snoqualmie River in Washington

This mayfly was collected from the South Fork Snoqualmie River in Washington on May 14th, 2022 and added to Troutnut.com by Troutnut on May 16th, 2022.


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References

  • Zloty, J and Pritchard, G. 1997. Larvae and adults of Ameletus mayflies (Ephemeroptera: Ameletidae) from Alberta. Canadian Entomologist 129: 251-289.

Ameletus cooki (Brown Dun) Mayfly Nymph Pictures

Collection details
Location: South Fork Snoqualmie River, Washington
Date: May 14th, 2022
Added to site: May 16th, 2022
Author: Troutnut
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