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Slate Brown Duns

Scientific Names
MatchScientific 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 NymphEpeorus (Little Maryatts) Mayfly Nymph View 9 Pictures
Collected May 6, 2007 from in
Added to Troutnut.com by on May 18, 2007
Male Epeorus (Little Maryatts) Mayfly DunMale Epeorus (Little Maryatts) Mayfly Dun View 12 PicturesI hoped this dun would molt into a spinner for a positive ID, but it didn't. My best guess is Epeorus dulciana, but that's only because that's the smallest western Epeorus species, and this specimen is smaller than any of the others, with a body length of 5.3 mm (although it would be longer as a spinner) and a wing length of 8.5 mm.

It was collected at the same time as a similar-sized female dun.
Collected July 5, 2017 from in
Added to Troutnut.com by on July 6, 2017
Male Epeorus albertae (Pink Lady) Mayfly SpinnerMale Epeorus albertae (Pink Lady) Mayfly Spinner View 14 Pictures
Collected July 11, 2017 from in
Added to Troutnut.com by on July 12, 2017

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 NymphEpeorus 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 SpinnerFemale 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
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