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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 Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington
I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing this one.
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.

Updates from September 3, 2020

Updates from September 3, 2020

Photos by Troutnut from Silver Creek and Trail Creek in Idaho

Silver Creek in Idaho
Silver Creek in Idaho
Silver Creek in Idaho
Silver Creek in Idaho
Silver Creek in Idaho
Silver Creek in Idaho
Silver Creek in Idaho
Trail Creek in Idaho
Trail Creek in Idaho
Trail Creek in Idaho

On-stream insect photos by Troutnut from Silver Creek in Idaho

Silver Creek in Idaho
Female Baetid spinners were abundant subsurface looking for substrates to lay their eggs, and they found my waders. I'll update the ID for this picture after identifying the associated male spinner. I caught several fish on a small brown soft-hackle fished as a crude imitation of these spinners before the fish all started taking Tricorythodes spinners instead.

From Silver Creek in Idaho

Closeup insects by Troutnut from Silver Creek in Idaho

Artistic view of a Female Callibaetis ferrugineus (Baetidae) (Speckled Dun) Mayfly Spinner from Silver Creek in Idaho
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
Some notes from identifying this specimen under the microscope:

1. The hind wing has three longitudinal veins, but the third is faint, short (about half the length of the wing), and close to the wing margin.
2. Then antenna is brown fading into white at the tip, and the base is ringed with white.
3. The joints of the tarsal segments on the middle and hind leg have fine black markings.

It was also collected in association with a female spinner.
Lateral view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
This female spinner was deceased when photographed, so the posture is unnatural, but it was a substantial hatch and clearly worth imitating (with wet flies to imitate the sunken ovipositing females) so I went ahead with the photos.

It was collected in association with a male spinner.

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Jun 28, 2007
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