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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Doroneuria baumanni (Golden Stone) Stonefly Nymph Doroneuria baumanni (Golden Stone) Stonefly Nymph

Dorsal view of a Doroneuria baumanni (Perlidae) (Golden Stone) Stonefly Nymph from Sears Creek in Washington

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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.

Stenonema femoratum (Cream Cahill) Mayfly Nymph Pictures

This one had a hitchhiker I didn't notice at first.

Stenonema femoratum (Heptageniidae) (Cream Cahill) Mayfly Nymph from Mongaup Creek in New York

This is the picture that shows why this is Stenonema instead of Maccaffertium. The main gills are rounded rather than truncate (square-ish) and the last, thread-like pair of gills is visibly tracheated (that little stripe through the center). Those characteristics distinguish Stenonema femoratum.

Stenonema femoratum (Heptageniidae) (Cream Cahill) Mayfly Nymph from Mongaup Creek in New York

Stenonema femoratum (Heptageniidae) (Cream Cahill) Mayfly Nymph from Mongaup Creek in New York

Ventral view of a Stenonema femoratum (Heptageniidae) (Cream Cahill) Mayfly Nymph from Mongaup Creek in New York

Dorsal view of a Stenonema femoratum (Heptageniidae) (Cream Cahill) Mayfly Nymph from Mongaup Creek in New York

Ruler view of a Stenonema femoratum (Heptageniidae) (Cream Cahill) Mayfly Nymph from Mongaup Creek in New York The smallest ruler marks are 1 mm.

This mayfly was collected from Mongaup Creek in New York on May 6th, 2007 and added to Troutnut.com by Troutnut on May 18th, 2007.

Discussions of this Nymph

Not Stenonema femoratum

4 replies

Posted by Dewalt on Jun 12, 2013

Last reply on Jun 12, 2013 by Entoman

Only Stenonema left in North America (after taxonomic revision) is S. femoratum. The underside of the abdomen has rows of roundish dark spots at the lateral margins. This one does not.

Finally my "Stenonema" section isn't empty

2 replies

Posted by Troutnut on May 18, 2007

Last reply on May 20, 2007 by Troutnut

I've been looking for one of these for a while. After I realized that everything I was calling Stenonema had been renamed to Maccaffertium, the section for this once-popular genus was empty. Now with this one from a small stream in the Catskills I'm pretty sure I've got an actual Stenonema again.

I would welcome a verification from those of you with more entomological training, but it looks right to me.

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