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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large brown trout that only touch streamers for the rest of the year.

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 Baetis tricaudatus (Blue-Winged Olive) Mayfly Dun Pictures

This female was associated with a male of the same species.

Lateral view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York
Ruler view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York The smallest ruler marks are 1 mm.
Dorsal view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York
Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York
Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York
Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York
Ventral view of a Female Baetis tricaudatus (Baetidae) (Blue-Winged Olive) Mayfly Dun from Owasco Inlet in New York

This mayfly was collected from Owasco Inlet in New York on April 3rd, 2007 and added to Troutnut.com by Troutnut on April 3rd, 2007.

Discussions of this Dun

Maybe tricaudatus
25 replies
Posted by GONZO on Apr 4, 2007
Last reply on Apr 10, 2007 by Konchu
Based on size, emergence timing, and general appearance, I'd guess that this and the associated male are probably B. tricaudatus.

Start a Discussion of Dun

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

Collection details
Location: Owasco Inlet, New York
Date: April 3rd, 2007
Added to site: April 3rd, 2007
Author: Troutnut
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