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Chocolate Duns

Like most common names, "Chocolate Dun" can refer to more than one taxon. They're previewed below, along with 7 specimens. For more detail click through to the scientific names.

Mayfly Genus Eurylophella

These are often called Chocolate Duns.
None of the species in this genus are recognized as significant hatches. Nevertheless, I have found their nymphs in my samples in many streams in both the East and Midwest.
Eurylophella temporalis (Chocolate Dun) Mayfly NymphEurylophella temporalis (Chocolate Dun) Mayfly Nymph View 9 Pictures
Collected June 5, 2005 from in
Added to Troutnut.com by on May 25, 2006
Male Eurylophella (Chocolate Duns) Mayfly DunMale Eurylophella (Chocolate Duns) Mayfly Dun View 5 Pictures
Collected June 14, 2005 from in
Added to Troutnut.com by on May 26, 2006
Male Eurylophella (Chocolate Duns) Mayfly SpinnerMale Eurylophella (Chocolate Duns) Mayfly Spinner View 10 Pictures
Collected June 4, 2005 from in
Added to Troutnut.com by on May 24, 2006

Mayfly Species Eurylophella bicolor

These are often called Chocolate Duns.
According to the Leonards in Mayflies: An Angler's Study of Trout Water Ephemeroptera , this species and Eurylophella bicolor are the two most likely hatches for fly fishermen to encounter in Michigan. Based on my sampling, it seems other species may be more prevalent elsewhere.

Mayfly Species Ephemerella needhami

These are very rarely called Chocolate Duns.
This small and slightly noteworthy mayfly appears during the finest hours of the year. Ernest Schwiebert describes an Ephemerella needhami day in Matching the Hatch:

"It was a wonderul morning, with a sky of indescribable blue and big, clean-looking cumulus clouds, and the water was sparkling and alive. You have seen the water with that lively look; you have also seen it dead and uninviting in a way that dampens the enthusiasm the moment you wade out into the current."


I have not fished a needhami emergence, but the exquisite nymphs show up often (though never abundantly) in my samples.
Ephemerella needhami (Little Dark Hendrickson) Mayfly NymphEphemerella needhami (Little Dark Hendrickson) Mayfly Nymph View 6 PicturesI photographed three strange striped Ephemerella nymphs from the same trip on the same river: this one, a brown one, and a very very striped one. I have tentatively put them all in Ephemerella needhami for now.
Collected June 9, 2005 from in
Added to Troutnut.com by on May 26, 2006
Ephemerella needhami (Little Dark Hendrickson) Mayfly DunEphemerella needhami (Little Dark Hendrickson) Mayfly Dun View 7 PicturesSee the comments for an interesting discussion of the identification of this dun.
Collected June 1, 2007 from in
Added to Troutnut.com by on June 4, 2007

Mayfly Species Ephemera simulans

These are very rarely called Chocolate Duns.
The Brown Drakes are a favorite hatch of many in the Midwest, and they make a good showing on localized waters across the country. They are usually the first in a series of big drakes which bring large trout to the surface at twilight and into the early hours of the night.
Ephemera simulans (Brown Drake) Mayfly NymphEphemera simulans (Brown Drake) Mayfly Nymph View 10 Pictures
Collected January 31, 2004 from in
Added to Troutnut.com by on January 25, 2006
Male Ephemera simulans (Brown Drake) Mayfly SpinnerMale Ephemera simulans (Brown Drake) Mayfly Spinner View 7 Pictures
Collected June 2, 2005 from in
Added to Troutnut.com by on May 24, 2006
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