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.

Ventral view of a Hydropsyche (Hydropsychidae) (Spotted Sedge) Caddisfly Larva from the Yakima River in Washington
With a bit of help from the microscope, this specimen keys clearly and unsurprisingly to Hydropsyche.
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.

American March Browns

Like most common names,"American March Brown" can refer to more than one taxon. They're previewed below, along with 5 specimens. For more detail click through to the scientific names.

Mayfly Species Stenonema vicarium

These are often called American March Browns.
In the East and Midwest this is one of the most important hatches of the Spring. They are large flies which emerge sporadically, making for long days of good fishing.

This species contains the two classic Eastern hatches formerly known as Stenonema vicarium and Stenonema fuscum, the "March Brown" and "Gray Fox." Entomologists have discovered that these mayflies belong to the same species, but they still display differences in appearance which the trout notice easily. Anglers should be prepared to imitate both types.
Artistic view of a Male Stenonema vicarium (Heptageniidae) (March Brown) Mayfly Dun from the Namekagon River in Wisconsin
I collected this mayfly on the same trip as a female of the same species. After these photos it molted into a spinner. This is the form of Stenonema vicarium which anglers call the "Gray Fox."
Lateral view of a Female Stenonema vicarium (Heptageniidae) (March Brown) Mayfly Spinner from the Namekagon River in Wisconsin
I collected this mayfly on the same trip as a male of the same species. They are Maccaffertium vicarium mayflies of the type formerly known as Stenonema fuscom, the "Gray Fox."
Dorsal view of a Stenonema vicarium (Heptageniidae) (March Brown) Mayfly Nymph from the Beaverkill River in New York

Mayfly Species Litobrancha recurvata

These are very rarely called American March Browns.
Litobrancha recurvata is generally reported to be the largest North American species of mayfly in angler entomologies, though this understanding is being challenged by reports of Hexagenia limbata that may exceed 40mm in some locales. Regardless, it is certainly the largest mayfly in the region of its distribution. Sometimes it appears together with species of Hexagenia or Ephemera, but in other places it creates excellent action on its own.
Female Litobrancha recurvata (Ephemeridae) (Dark Green Drake) Mayfly Dun from the Au Sable River (Mainstream) in Michigan
These photos were contributed by Spencer Vanderhoof.
Male Litobrancha recurvata (Ephemeridae) (Dark Green Drake) Mayfly Spinner from the Au Sable River (Mainstream) in Michigan
These photos were contributed by Spencer Vanderhoof.

American March Browns

Troutnut.com is copyright © 2004-2024 (email Jason). privacy policy