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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.

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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This topic is about the Mayfly Genus Ephemerella

This genus contains the legendary Hendricksons and Sulphurs of the East and the equally important Pale Morning Duns of western waters.

No scientific name in American angling literature is more renowned and at the same time capable of more confusion than the genus name "Ephemerella." It is important that anglers have a good overall grasp of its taxonomic history if they are to make any sense out of the rich literary heritage involving this mayfly name.

By the time American angling literature began to take serious note of entomology in the decades of the early to mid 20th century, Ephemerella was considered a "super-genus" in the family Baetidae, containing all of the important species to anglers in the subfamily Ephemerellinae. Taxonomists organized them by association with "type" species that were referred to as "groups" within this very large and unruly genus.

This organizational structure held sway until the 70's when they were recognized as separate from the Baetidae with their own family, the Ephemerellidae. The "groups" (after a little name changing and reorganization) were given subgenus status, but in conformance with taxonomical convention,the nomenclature retained the use of the name Ephemerella when referring to individual species genus status. More change occurred towards the end of the century as consensus formed around the subgenera achieving full generic status. The broad use of Ephemerella was then dropped in favor of the new generic names.

These changes were necessary in that they addressed many problems exposed in older taxonomies. Unfortunately, all during this period the changes were reported with varying degrees of accuracy and acceptance. For anglers this was exacerbated by the continued use and reliance on older entomology texts in many circles. Be that as it may, recent or updated angler entomologies now recognize that many of the old Ephemerella species are spread out among several genera in the Ephemerellidae family. These include the various Blue-Winged Olives and Western Green Drakes of the Drunella genus as well as several important species scattered in genera like Attenella and Serratella, to name a few.

Despite these revisions in classification, the Ephemerella genus still contains arguably the most important species in North America, and remains a "super-genus" to anglers.

There is a lot of variation; refer to the genus species hatch pages for details.

Example specimens

Posts: 1
Alisadeq on May 14, 2008May 14th, 2008, 12:51 am EDT
on the long time am looking for akey to mayflies (larvae) please if you have any information about this subject you can send it to me on my


thank you
Taxon's profile picture
Site Editor
Plano, TX

Posts: 1311
Taxon on May 14, 2008May 14th, 2008, 4:24 am EDT

For what geographic location, North America, or somewhere else? For which taxonomic group, only Ephemerella, or all of Ephemeroptera? For what taxonomic levels, family, genus, or species?

Taxonomic keys for mayfly larvae (nymphs) would differ significantly between continents, particularly below family level. For example, probably over 50% percent of the genera present on the European continent, are not present on the N. American continent, and vice versa. And, at the species level, there would be virtually no commonality.
Best regards,
Roger Rohrbeck
Troutnut's profile picture
Bellevue, WA

Posts: 2758
Troutnut on May 15, 2008May 15th, 2008, 3:12 pm EDT
He sent me an email about this, too, and said he's looking for a key to the mayfly and stonefly nymphs of Iraq. I don't know any... does anyone here?
Jason Neuswanger, Ph.D.
Troutnut and salmonid ecologist
Konchu's profile picture
Site Editor

Posts: 498
Konchu on May 15, 2008May 15th, 2008, 3:23 pm EDT
I'm not aware of a key, but there is a 20-yr old list of Ephemeroptera from Iraq.

Al-Zubaidi F; Braasch D; Al-Kayatt A. 1987. Mayflies from Iraq (Insecta, Ephemeroptera). Faunistische Abhandlungen Staatliches Museum für Tierkunde Dresden 14:179-184.

A pdf-file is available from Michael Hubbard and his Florida A&M colleagues at the following URL.


Some of the terminology and classification is out-of-date, but it at least is a start towards narrowing the list of possibilities.

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