Header image
Enter a name
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 Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
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.

Male Ephemerella excrucians (Pale Morning Dun) Mayfly Dun Pictures

Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho
Dorsal view of a Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho
Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho
Ventral view of a Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho
Ruler view of a Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho The smallest ruler marks are 1 mm.
Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho
Lateral view of a Male Ephemerella excrucians (Ephemerellidae) (Pale Morning Dun) Mayfly Dun from the Henry's Fork of the Snake River in Idaho

This mayfly was collected from the Henry's Fork of the Snake River in Idaho on July 31st, 2020 and added to Troutnut.com by Troutnut on August 17th, 2020.

Discussions of this Dun

Ventral view
1 replies
Posted by Martinlf on Sep 5, 2020
Last reply on Sep 6, 2020 by Troutnut
Love the ventral photo. One guide ties duns with green abdomens and a bit of orange in the thorax. I see why now. Super photos.
Public service announcement: PMDs aren't yellow
13 replies
Posted by Troutnut on Aug 17, 2020
Last reply on Aug 28, 2020 by Wiflyfisher
It seems like most of the imitations I see in fly shops for PMDs, and dubbing mixes or other body materials designed to imitate PMDs, are a pale yellow color. I would just like to use this specimen to point out that in many cases (or in all the cases I've seen), most true PMDs (Ephemerella excrucians) are not yellow, but olive (with a bit of a gold tinge). I have some René Harrop PMD dubbing with the appropriate olive cast, but other than that I'm just seeing a lot of pale yellow more suited to eastern sulphur mayflies than excrucians.

The label PMD also applies to Ephemerella dorothea infrequens, but it seems they're also green as duns, unless I misidentified that specimen by associating an excrucians dun with nearby dorothea spinners.

Start a Discussion of Dun

References

Male Ephemerella excrucians (Pale Morning Dun) Mayfly Dun Pictures

Collection details
Location: Henry's Fork of the Snake River, Idaho
Date: July 31st, 2020
Added to site: August 17th, 2020
Author: Troutnut
Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy