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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 Neoleptophlebia (Leptophlebiidae) Mayfly Nymph from the Yakima River in Washington
Some characteristics from the microscope images for the tentative species id: The postero-lateral projections are found only on segment 9, not segment 8. Based on the key in Jacobus et al. (2014), it appears to key to Neoleptophlebia adoptiva or Neoleptophlebia heteronea, same as this specimen with pretty different abdominal markings. However, distinguishing between those calls for comparing the lengths of the second and third segment of the labial palp, and this one (like the other one) only seems to have two segments. So I'm stuck on them both. It's likely that the fact that they're immature nymphs stymies identification in some important way.
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 bicaudatus (BWO) Mayfly Nymph Pictures

This specimen was collected along with a female which was quite a bit larger, different in color, but otherwise seemed the same morphologically.

Lateral view of a Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington
Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington
Dorsal view of a Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington
Ventral view of a Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington
Ventral view of a Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington
Ruler view of a Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington The smallest ruler marks are 1 mm.
The darkened hind wing pad is clearly visible in this one.

Male Baetis bicaudatus (Baetidae) (BWO) Mayfly Nymph from Holder Creek in Washington

This mayfly was collected from Holder Creek in Washington on April 12th, 2021 and added to Troutnut.com by Troutnut on April 13th, 2021.


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Male Baetis bicaudatus (BWO) Mayfly Nymph Pictures

Collection details
Location: Holder Creek, Washington
Date: April 12th, 2021
Added to site: April 13th, 2021
Author: Troutnut
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