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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 Male Baetidae (Blue-Winged Olive) Mayfly Dun from Mystery Creek #308 in Washington
This dun emerged from a mature nymph on my desk. Unfortunately its wings didn't perfectly dry out.
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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Millcreek has attached these 5 pictures. The message is below.
Healdsburg, CA

Posts: 344
Millcreek on May 6, 2017May 6th, 2017, 2:39 pm EDT
I've submitted pictures of these before but Kogotus/Rickera wasn't as far along in it's instars and there weren't any live pictures of Isoperla mormona.

Kogotus/Rickeri can be found here:

Isoperla mormona can be found here:

The first three pictures are of Kogotus/Rickeri and the last two are of Isoperla mormona.
"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein
Crepuscular's profile picture
Boiling Springs, PA

Posts: 920
Crepuscular on May 9, 2017May 9th, 2017, 3:06 am EDT
Nice. Thanks for posting!
Jmd123's profile picture
Oscoda, MI

Posts: 2474
Jmd123 on May 9, 2017May 9th, 2017, 12:57 pm EDT
Wonderful pictures as always, Mark. Beautiful creatures up-close too! Thanks for sharing.

No matter how big the one you just caught is, there's always a bigger one out there somewhere...
Oldredbarn's profile picture
Novi, MI

Posts: 2600
Oldredbarn on May 11, 2017May 11th, 2017, 4:16 am EDT

Talk to me about the second from last pic...The littler one in the group. Different hatch years? Is this stone on a two year hatch cycle?

I have found Hex nymphs in our Manistee that are like that. One a larger size and another half as big. I assumed that one was slated to hatch the following year (I found them after Labor Day), and the smaller one the years after?

"Even when my best efforts fail it's a satisfying challenge, and that, after all, is the essence of fly fishing." -Chauncy Lively

"Envy not the man who lives beside the river, but the man the river flows through." Joseph T Heywood
Healdsburg, CA

Posts: 344
Millcreek on May 11, 2017May 11th, 2017, 12:12 pm EDT
Eric and Jonathan - Thanks for the kind words.

Spence - The latest word I've found has been that no one knows for sure but for Isoperla nymphs it's generally assumed that it's one year. I would guess that the smaller one will transform this year. It may also be a male, they tend to be smaller than the females.

As for the Kogotus/Rickeri no one has checked out it's time for remaining a nymph or at least I'm unable to find anything.

"If we knew what it was we were doing, it would not be called research, would it?"
-Albert Einstein

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