Slate Brown Duns

Mayflies

Caddisflies

Stoneflies

Scientific Names

Match	Scientific Name
	Epeorus
	Epeorus longimanus

Like most common names, "Slate Brown Dun" 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 Genus Epeorus

These are sometimes called Slate Brown Duns.

There is remarkable variety of form and color within this prolific genus of fast-water mayflies. Different species are found across the country, and several cause good hatches. Fly anglers are likely to encounter the lesser species on occasion, too.

The best Epeorus hatch in the East is Epeorus pleuralis, the famous Quill Gordon, the first abundant large mayfly hatch of the year. Epeorus vitreus comes a little later and is important in both the East and Midwest.

In the West, Epeorus longimanus dominates in fast, high-altitude streams, while Epeorus albertae inhabits slower and lower waters.

Epeorus (Little Maryatts) Mayfly Nymph

View 9 Pictures

Collected May 6, 2007 from in
Added to Troutnut.com by on May 18, 2007

Male Epeorus pleuralis (Quill Gordon) Mayfly Dun

View 9 PicturesI kept this specimen after photographing it and it molted into a spinner in perfect condition, which I photographed here.

Collected April 30, 2007 from in
Added to Troutnut.com by on May 3, 2007

Male Epeorus pleuralis (Quill Gordon) Mayfly Spinner

View 10 PicturesI spent (Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.) most of the day looking for Epeorus pluralis duns or spinners without any luck on the major Catskill rivers. Finally in the evening I arrived at a small stream somebody had recommended, and when I got out of the car I was happy to find that I had parked in the middle of a cloud of male spinners.

Collected April 19, 2006 from in
Added to Troutnut.com by on April 22, 2006

See 49 more specimens...

Mayfly Species Epeorus longimanus

These are sometimes called Slate Brown Duns.

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

Epeorus longimanus (Slate Brown Dun) Mayfly Nymph

View 2 Pictures

Collected June 24, 2005 from in
Added to Troutnut.com by 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 in
Added to Troutnut.com by on July 25, 2011

See 3 more specimens...

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.

Spent: The wing position of many aquatic insects when they fall on the water after mating. The wings of both sides lay flat on the water. The word may be used to describe insects with their wings in that position, as well as the position itself.

Spinner: There are two winged stages of adult mayflies. They emerge from the water as duns, molt on land (usually) into their fully mature stage, spinners. As spinners, they mate, lay eggs, and die.