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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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Dorsal view of a Gomphidae Dragonfly Nymph from the Namekagon River in Wisconsin
Waxsmith
CANADA

Posts: 6
Waxsmith on Feb 11, 2011February 11th, 2011, 2:26 pm EST
I do know these nymphs are biggies alright, but just what is the average size of them, like their length in "mm"?
What is this supposed to look like, example please.
Taxon
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on Feb 11, 2011February 11th, 2011, 4:33 pm EST
A.K.-

According to McCafferty, Gomphid (Clubtail) nymphs generally measure from 23-40 mm. (and rarely as long as 65 mm.) at maturity.
Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com

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