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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.

Dorsal view of a Glossosoma (Glossosomatidae) (Little Brown Short-horned Sedge) Caddisfly Larva from the Yakima River in Washington
I caught this tiny larva without a case, but it seems to key pretty clearly to to Glossosomatidae. From there, the lack of sclerites on the mesonotum points to either Glossosoma or Anagapetus. Although it's difficult to see in a 2D image from the microscope, it's pretty clear in the live 3D view that the pronotum is only excised about 1/3 of its length to accommodate the forecoxa, not 2/3, which points to Glossosoma at Couplet 5 of the Key to Genera of Glossosomatidae Larvae.
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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Male Baetis tricaudatus (Blue-Winged Olive) Mayfly Nymph Pictures

This specimen and many like it were found with other specimens I found to be duller-colored females of the same species. I wasn't aware of such a difference between male and female nymphs in Baetids, but all the morphological characteristics I checked in the key were the same, and the color patterns are, too -- just not the brightness.

Ruler view of a Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington The smallest ruler marks are 1 mm.
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Ventral view of a Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Dorsal view of a Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Nymph from the Yakima River in Washington
Detached labium and labial palps.

Male Baetis tricaudatus (Baetidae) (Blue-Winged Olive) 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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Male Baetis tricaudatus (Blue-Winged Olive) 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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