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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.
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.

Mayfly Family Caenidae (Angler's Curses)

The tiny mayflies of this family are usually found in warm, slow, marginal trout water, although some trout streams hold good populations too.

The only genus ever known to produce fishable hatches is Caenis. It turns up frequently for anglers who sample nymphs, but it is rarely of any practical importance for fly fishing because its emergence traits and tiny size (even smaller than Tricorythodes) make it relatively unimportant.

Brachycercus is even more focused on warm water than Caenis.

Taxonomic History

Some relatively common trout stream species formerly known in Brachycercus were recently reclassified into Sparbarus and Susperatus.

Where & when

In 327 records from GBIF, adults of this family have mostly been collected during July (29%), June (25%), August (24%), May (10%), and September (8%).

In 153 records from GBIF, this family has been collected at elevations ranging from 26 to 8022 ft, with an average (median) of 2789 ft.

Family Range


To determine whether a specimen of Ephemeroptera belongs to Caenidae, use the Key to Families of Mayfly Nymphs or Key to Families of Mayfly Duns and Spinners.

Specimens of the Mayfly Family Caenidae

1 Female Dun
1 Female Spinner
9 Nymphs

Discussions of Caenidae

Start a Discussion of Caenidae


Mayfly Family Caenidae (Angler's Curses)

Genus in Caenidae: Brachycercus, Caenis
5 genera (Amercaenis, Cercobrachys, Latineosus, Sparbarus, and Susperatus) aren't included.
Family Range
Common Name
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