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.

Stream photos

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Hydropsyche (Spotted Sedge) Caddisfly Larva Hydropsyche (Spotted Sedge) Caddisfly Larva

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Larva from the Yakima River in Washington

With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.

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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.

Biggest Mayfly

Al514

Central New York

Posts: 142

Al514 on Sep 17, 2007September 17th, 2007, 2:29 pm EDT

What is the biggest mayfly species in the North East? I was at a 7 to 8 acre pond tonight that holds some nice trout, and I swear I saw some spinners about size 8 or 6! I had to do a double-take to make sure it was a mayfly! I didnt have my camera, so no pictures but Ill try and get some soon. It looked dark brown and around 2, possibly 3 inches in length.

Al514

Central New York

Posts: 142

Al514 on Sep 17, 2007September 17th, 2007, 2:32 pm EDT

Ok, so I originally thought it was Hex, but I didn't think they were that big. After looking at the pictures on here, I'm sure it was a Hex.

Taxon

Site Editor
Plano, TX

Posts: 1311

Taxon on Sep 17, 2007September 17th, 2007, 3:45 pm EDT

There are only three mayfly genera with really large mayflies, which I would describe as being in excess of 1" in length, as measured from the front of head to end of abdomen, exclusive of tails.

These are Ephemera, Hexagenia, and Litobrancha, all burrowers in family Ephemeridae. Of those three genera, only Hexagenia are found in ponds.

Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com

Troutnut

Administrator
Bellevue, WA

Posts: 2758

Troutnut on Sep 17, 2007September 17th, 2007, 7:17 pm EDT

At this time of year, it was probably a different species of Hex, like Hexagenia atrocaudata. Check out the pics of that one on this site and see if they match a little closer still.

Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist