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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Limnephilus (Summer Flier Sedge) Caddisfly Larva Limnephilus (Summer Flier Sedge) Caddisfly Larva

Case view of a Limnephilus (Limnephilidae) (Summer Flier Sedge) Caddisfly Larva from the Yakima River 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.

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Male Rhithrogena hageni (Western Black Quill) Mayfly Spinner Pictures

Although I could not find the preserved specimen to examine under my good new microscope, I'm tentatively calling it one Rhithrogena hageni, based on apparent similarity to this specimen, which I was able to positively ID.

The relative angle of the penes is a bit shallower in this specimen, but I photographed another specimen from the same collecting trip (and I think even the same swarm, although I don't recall for sure) as the other one, and it had the shallower angle seen on this specimen. I'm guessing it's just variation within the species.

Lateral view of a Male Rhithrogena hageni (Heptageniidae) (Western Black Quill) Mayfly Spinner from the Ruby River in Montana

Male Rhithrogena hageni (Heptageniidae) (Western Black Quill) Mayfly Spinner from the Ruby River in Montana

Dorsal view of a Male Rhithrogena hageni (Heptageniidae) (Western Black Quill) Mayfly Spinner from the Ruby River in Montana

Ventral view of a Male Rhithrogena hageni (Heptageniidae) (Western Black Quill) Mayfly Spinner from the Ruby River in Montana

Ruler view of a Male Rhithrogena hageni (Heptageniidae) (Western Black Quill) Mayfly Spinner from the Ruby River in Montana The smallest ruler marks are 1 mm.

This mayfly was collected from the Ruby River in Montana on July 8th, 2019 and added to Troutnut.com by Troutnut on July 18th, 2019.

Discussions of this Spinner

Puzzled on this mayfly, not even confident on family

1 replies

Posted by Troutnut on Jul 22, 2019

Last reply on Jul 23, 2019 by Millcreek

This seems to be some sort of Heptageniid, based on the two tails and five segments on the hind tarsus. Following the key in Merritt & Cummins seems to lead to Rhithrogena, but it doesn't fit a characteristic described in Needham's Biology of Mayflies for that genus: "Tibia of hind leg in both sexes about 1/4 length of femur."

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