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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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Female Baetis tricaudatus (Blue-Winged Olive) Mayfly Spinner Pictures

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.

Lateral view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
Dorsal view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
Ventral view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho
Ruler view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Spinner from Silver Creek in Idaho The smallest ruler marks are 1 mm.

This mayfly was collected from Silver Creek in Idaho on September 4th, 2020 and added to Troutnut.com by Troutnut on September 18th, 2020.


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Female Baetis tricaudatus (Blue-Winged Olive) Mayfly Spinner Pictures

Collection details
Location: Silver Creek, Idaho
Date: September 4th, 2020
Added to site: September 18th, 2020
Author: Troutnut
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