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.

A trackless paradise two days deep in the Yellowstone backcountry

From Mystery Creek # 218 in Wyoming

Stream photos

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Sweltsa (Sallfly) Stonefly Nymph Sweltsa (Sallfly) Stonefly Nymph

Dorsal view of a Sweltsa (Chloroperlidae) (Sallfly) Stonefly Nymph from the Yakima River in Washington

This species was fairly abundant in a February sample of the upper Yakima.

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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.

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.

Caddisfly Species Brachycentrus numerosus (Dark Grannoms)

In Caddisflies, Gary LaFontaine attributed the famous spring hatch on the Beaverkill (now known as the "Apple Caddis") to this species. After that publication, entomologists described that major hatch as a new species -- Brachycentrus appalachia.

Brachycentrus numerosus is probably still important in many locations.

Where & when

Time of year : May

In 18 records from GBIF, adults of this species have been collected during April (33%), May (33%), June (17%), March (11%), and July (6%).

In 8 records from GBIF, this species has been collected at elevations ranging from 750 to 5381 ft, with an average (median) of 4921 ft.

Species Range

source

Map of specific collection sites

Hatching behavior

Time of day : Afternoon

Egg-Laying behavior

Time of day: Evening

Special thanks to Lloyd Gonzales, author of the excellent new book Fly-Fishing Pressured Water, for helping to sort out the Brachycentrus species and common names.

Start a Discussion of Brachycentrus numerosus

References

Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.
Gonzales, Lloyd. 2005. Fly-Fishing Pressured Water. Stackpole Books.
LaFontaine, Gary. 1981. Caddisflies. The Lyons Press.