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.

I caught several wild and colorful 8-9 inch brook trout in the clear little pool below this waterfall.

From Mystery Creek # 89 in New York

Stream photos

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Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva Onocosmoecus (Great Late-Summer Sedge) Caddisfly Larva

Lateral view of a Onocosmoecus (Limnephilidae) (Great Late-Summer Sedge) Caddisfly Larva from the Yakima River in Washington

This specimen keys pretty easily to Onocosmoecus, and it closely resembles a specimen from Alaska which caddis expert Dave Ruiter recognized as this genus. As with that specimen, the only species in the genus documented in this area is Onocosmoecus unicolor, but Dave suggested for that specimen that there might be multiple not-yet-distinguished species under the unicolor umbrella and it would be best to stick with the genus-level ID. I'm doing the same for this one.

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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.

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Male Eurylophella minimella (Chocolate Dun) Mayfly Spinner Pictures

The genus ID on this specimen is confident but species is very tentative, based on the tentative ID of a seemingly-identical specimen from a nearby river a few days apart.

Lateral view of a Male Eurylophella minimella (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the Namekagon River in Wisconsin

Male Eurylophella minimella (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the Namekagon River in Wisconsin

Ventral view of a Male Eurylophella minimella (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the Namekagon River in Wisconsin

Dorsal view of a Male Eurylophella minimella (Ephemerellidae) (Chocolate Dun) Mayfly Spinner from the Namekagon River in Wisconsin

This mayfly was collected from the Namekagon River in Wisconsin on June 3rd, 2005 and added to Troutnut.com by Troutnut on May 24th, 2006.

Discussions of this Spinner

Not invaria

2 replies

Posted by GONZO on May 24, 2009

Last reply on May 24, 2009 by GONZO

This spinner is Eurylophella rather than E. invaria. The long 9th abdominal segment of Eurylophella is often the easiest way to avoid confusing the duns and spinners with Ephemerella. The claspers and genitalia of this male are also representative of Eurylophella.

Invaria Spinners

10 replies

Posted by Martinlf on Aug 9, 2007

Last reply on Aug 10, 2007 by JAD

These photos show a darker invaria spinner than I'm used to seeing. I know color varies a good bit in invaria nymphs and duns, so I suppose color variation is pretty wide with the spinners also, correct?

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