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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.

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.
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Rhithrogena virilis Mayfly Nymph Pictures

I'm tentatively calling this specimen Rhithrogena virilis, based on the incomplete key in The Biology of Mayflies which describes the correct body length (12 mm) and a purplish tinge on the dorsal half of the platelike gills. An early specimen posted by Bob Newell describes markings on the last couple abdominal tergites which also match this nymph.

Ruler view of a Rhithrogena virilis (Heptageniidae) Mayfly Nymph from the Yakima River in Washington The smallest ruler marks are 1 mm.
Ventral view of a Rhithrogena virilis (Heptageniidae) Mayfly Nymph from the Yakima River in Washington
Dorsal view of a Rhithrogena virilis (Heptageniidae) Mayfly Nymph from the Yakima River in Washington

This mayfly was collected from the Yakima River in Washington on April 24th, 2022 and added to Troutnut.com by Troutnut on April 27th, 2022.


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References

  • Needham, James G., Jay R. Traver, and Yin-Chi Hsu. 1935. The Biology of Mayflies. Comstock Publishing Company, Inc.

Rhithrogena virilis Mayfly Nymph Pictures

Collection details
Location: Yakima River, Washington
Date: April 24th, 2022
Added to site: April 27th, 2022
Author: Troutnut
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