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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.

Dorsal view of a Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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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Male Stenonema (March Browns and Cahills) Mayfly Dun Pictures

I collected this male dun together with a female.

Lateral view of a Male Stenonema (Heptageniidae) (March Browns and Cahills) Mayfly Dun from the Namekagon River in Wisconsin
Male Stenonema (Heptageniidae) (March Browns and Cahills) Mayfly Dun from the Namekagon River in Wisconsin
Male Stenonema (Heptageniidae) (March Browns and Cahills) Mayfly Dun from the Namekagon River in Wisconsin
Male Stenonema (Heptageniidae) (March Browns and Cahills) Mayfly Dun from the Namekagon River in Wisconsin
Male Stenonema (Heptageniidae) (March Browns and Cahills) Mayfly Dun from the Namekagon River in Wisconsin
Ventral view of a Male Stenonema (Heptageniidae) (March Browns and Cahills) Mayfly Dun from the Namekagon River in Wisconsin

This mayfly was collected from the Namekagon River in Wisconsin on May 27th, 2005 and added to Troutnut.com by Troutnut on May 22nd, 2006.


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Male Stenonema (March Browns and Cahills) Mayfly Dun Pictures

Collection details
Location: Namekagon River, Wisconsin
Date: May 27th, 2005
Added to site: May 22nd, 2006
Author: Troutnut
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