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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.

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.

Adirman's profile picture
Monticello, NY

Posts: 479
Adirman on Aug 30, 2010August 30th, 2010, 6:55 am EDT


I was wondering if someone could give me some tips/pointers on basic id'ing. for the 1st several yrs I flyfished, I ignored that aspect fo the sport and focused on casting, rigging, knots, etc. Know that i'm more proficient in those other areas, I want to get better at id'ing the bugs! I'm sure i can tell caddis from mayflies and spinnersIin most cases) from duns but its hard for me to sort out the nymphs. Example, yesterday, me and a buddy went fishing and he pointed out to me all the empty Iso shucks from the nymphs emerging. When I looked at them, the color looked right(sorta brownish red?)but honestly, they kinda looked like stoneflies as well. Any easy way to tell the difference?

Site Editor
"Bear Swamp," PA

Posts: 1681
GONZO on Aug 30, 2010August 30th, 2010, 8:05 am EDT
Any easy way to tell the difference?

Yes. Stonefly nymphs will typically have two wingcases (one behind the other) and two tails. Isonychia nymphs will appear to have one wingcase (they have a second to house the smaller hindwings, but it is hidden under the first) and three (fringed) tails. Although Isonychia nymphs have rather long antennae for a mayfly, they are not as conspicuous as most stonefly antennae.

As a general guide to some of the easily observable differences, this link to Roger's website should help:

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