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**Mayfly Species Epeorus longimanus (Slate Brown Dun)**

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Heptageniidae (March Browns, Cahills, Quill Gordons)

» Genus Epeorus (Little Maryatts)

» Species longimanus (Slate Brown Dun)

Common Names

Match	Common Name
	Slate Brown Dun
	Western Gordon Quill
	Red Quill Spinner
	Quill Gordon

Pictures Below ↓

Epeorus longimanus and Epeorus albertae are the two most common Epeorus species in the West.

Where & When

Region: West

Time Of Year (?): June through mid-August, peaking in mid-June to mid-July, for about one week in any given location

Altitude: Above 5,000 feet

According to Ernest Schweibert in Matching the Hatch, the trout "respond very well" to this hatch. Fred Arbona in Mayflies, the Angler, and the Trout called the hatches disappointing, noting that they may be overshadowed by simultanenous hatches of Rhithrogena hageni.

Hatching Behavior

Time Of Day (?): Anytime; sometimes concentrated in late morning

The nymphs emerge sporadically on the bottom in the shallows and rise to the surface as duns.

Spinner Behavior

Time Of Day: Midday

Habitat: Fast water

Nymph Biology

Current Speed: Fast

This species is found more in the cold headwaters than Epeorus albertae and Epeorus grandis.

Pictures of 5 Mayfly Specimens in the Species Epeorus longimanus:

Specimen Page:12

Epeorus longimanus (Slate Brown Dun) Mayfly Nymph

View 2 Pictures

Collected June 24, 2005 from the Vermillion River in Montana
Added to Troutnut.com by Bnewell on June 27, 2011

Female Epeorus longimanus (Slate Brown Dun) Mayfly Spinner

View 1 PicturesI associated this female with a male I collected one night later. For a great and informative discussion of all Epeorus species and other mayflies be sure and read, WESTERN MAYFLY HATCHES by R. Hafele and D. Hughes. They rate all of the western mayflies and they rate the hatch of this genus a 25 out of a possible 45 points based on several rating criterion. They provide insect photos, possible fly patterns and fly presentations. This is a great book.

Collected July 24, 2011 from the Touchet River in Washington
Added to Troutnut.com by Bnewell on July 25, 2011

Epeorus longimanus (Slate Brown Dun) Mayfly Nymph

View 9 Pictures

Collected July 4, 2020 from Mystery Creek #249 in Washington
Added to Troutnut.com by Troutnut on July 12, 2020

Specimen Page:12

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Jargon Defined:

Duns: Mayflies have two adult stages. They first emerge from the water as duns (scientifically known as the subimago stage). They then molt into the spinner (imago) stage, in which they mate and die. Sometimes the word "dun" is confusingly used to refer to a brownish gray color in fly tying materials.

Nymphs: The juvenile, underwater stages of mayflies, stoneflies, dragonflies, and damselflies and other aquatic insects whose juvenile stages are covered by hard exoskeletons. The word can also refer to the fishing flies which imitate these creatures, in which case it is used as a blanket term for flies imitating any underwater stage of an invertebrate (except for crayfish and leeches).

Useful References:

Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.

Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.

Schwiebert, Ernest G. 1955. Matching the Hatch. MacMillan Publishing Company.

Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.