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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Ephemerella mucronata Mayfly Nymph Ephemerella mucronata Mayfly Nymph

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.

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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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Taxonomy question

This topic is about the Mayfly Family Leptohyphidae

Read about the Tricorythodes genus for details. It is very important to trout anglers and it's the only significant trout stream genus in this family.

Most of the other genera are found only in warm waters in Mexico and the Southwest.

Example specimens

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Female Tricorythodes (Trico) Mayfly Spinner

Lateral view of a Female Tricorythodes (Leptohyphidae) (Trico) Mayfly Spinner from the Bitterroot River in Montana

This female Trico was collected with an associated male and many others.

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Male Tricorythodes (Trico) Mayfly Spinner

Lateral view of a Male Tricorythodes (Leptohyphidae) (Trico) Mayfly Spinner from the Bitterroot River in Montana

This specimen was collected along with a female. The forewing venation and styliger plate of the male give a confident identification as Tricorythodes explicatus according to Baumgardner 2009.

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Tricorythodes (Trico) Mayfly Nymph

Dorsal view of a Tricorythodes (Leptohyphidae) (Trico) Mayfly Nymph from Mystery Creek #308 in Washington

Doublezz105
Posts: 4

Doublezz105 on Oct 29, 2009October 29th, 2009, 10:46 am EDT

I have two keys (Pekarsky et al and Merrit and Cummins) listing Tricorythodes in the tricorythidae family, but Troutnut and Voshell show tricorythodes in the leptohyphidae family. Has tricorythodes been moved to leptohyphidae or vice versa?

Taxon

Site Editor
Plano, TX

Posts: 1311

Taxon on Oct 29, 2009October 29th, 2009, 11:58 am EDT

Doublezz105: I have two keys (Pekarsky et al and Merrit and Cummins) listing Tricorythodes in the tricorythidae family, but Troutnut and Voshell show tricorythodes in the leptohyphidae family. Has tricorythodes been moved to leptohyphidae or vice versa?

I believe acceptance of family Leptohyphidae dates to 2000, as described in Generic Revision of the North and Central American Leptohyphidae (Ephemeroptera: Pannota) by Wiersema and McCafferty.

The publication date of Aquatic Insects Of North America (Third Edition) by Merritt and Cummins is 1997. And, Freshwater macroinvertebrates of Northeastern North America by Pekarsky et al was published in 1990. So, both publications would have still listed genus Tricorythodes under family Tricorythidae.

Best regards,
Roger Rohrbeck
www.FlyfishingEntomology.com

Konchu

Site Editor
Indiana

Posts: 498

Konchu on Oct 30, 2009October 30th, 2009, 5:33 am EDT

taxon, check out mccafferty and wang's 2000 paper about pannote mayflies; they should give a history of the family leptohyphidae in there

Doublezz105
Posts: 4

Doublezz105 on Oct 30, 2009October 30th, 2009, 5:46 am EDT

Thanks so much for the speedy responses. And a special thanks for the link to the Wiersema & McCafferty paper. I thought it might be a taxonomy change since the publication of the keys, but I figured I'd check with some experts!