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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.
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Female Isonychia bicolor (Mahogany Dun) Mayfly Dun Pictures

I thought this dun was worth photographing, even though she's in pretty bad shape, because she shows something I haven't seen in Isonychia elsewhere. The bright stripe down the back which is normally present only in the nymph carried over to the dun in this one.

Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from Penn's Creek in Pennsylvania
Lateral view of a Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from Penn's Creek in Pennsylvania
Dorsal view of a Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from Penn's Creek in Pennsylvania
Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from Penn's Creek in Pennsylvania
Ruler view of a Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from Penn's Creek in Pennsylvania The smallest ruler marks are 1 mm.
Ventral view of a Female Isonychia bicolor (Isonychiidae) (Mahogany Dun) Mayfly Dun from Penn's Creek in Pennsylvania

This mayfly was collected from Penn's Creek in Pennsylvania on May 26th, 2007 and added to Troutnut.com by Troutnut on June 4th, 2007.


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Female Isonychia bicolor (Mahogany Dun) Mayfly Dun Pictures

Collection details
Location: Penn's Creek, Pennsylvania
Date: May 26th, 2007
Added to site: June 4th, 2007
Author: Troutnut
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