Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York

Blue-winged Olives
Baetis

Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Sunlight perfectly strikes the trees at a bend in the Foss River in the Washington Cascades.

From the Foss River in Washington

Stream photos

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Female Sweltsa borealis (Boreal Sallfly) Stonefly Adult Female Sweltsa borealis (Boreal Sallfly) Stonefly Adult

Lateral view of a Female Sweltsa borealis (Chloroperlidae) (Boreal Sallfly) Stonefly Adult from Harris Creek in Washington

I was not fishing, but happened to be at an unrelated social event on a hill above this tiny creek (which I never even saw) when this stonefly flew by me. I assume it came from there. Some key characteristics are tricky to follow, but process of elimination ultimately led me to Sweltsa borealis. It is reassuringly similar to this specimen posted by Bob Newell years ago. It is also so strikingly similar to this nymph from the same river system that I'm comfortable identifying that nymph from this adult. I was especially pleased with the closeup photo of four mites parasitizing this one.

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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.

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Male Afghanurus inconspicua Mayfly Dun Pictures

This pretty little dun was part of a sparse midsummer evening hatch on a large Catskill river.

I could not identify it by following a species key step by step, but I tentatively keyed it to the genus Nixe, and based on distribution maps and physical descriptions the most likely species is Nixe inconspicua. (Edit in 2023: this species was recently moved from Nixe into Afghanurus.)

Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York

Ventral view of a Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York

Ruler view of a Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York The smallest ruler marks are 1/16".

Dorsal view of a Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York

Lateral view of a Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York

The ratio of segment lengths on the tarsus of this dun is a helpful identifying characteristics.

Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York

Artistic view of a Male Afghanurus inconspicua (Heptageniidae) Mayfly Dun from the East Branch of the Delaware River in New York

This mayfly was collected from the East Branch of the Delaware River in New York on July 13th, 2005 and added to Troutnut.com by Troutnut on April 14th, 2006.

Discussions of this Dun

Maybe Epeorus

16 replies

Posted by Troutnut on Jul 5, 2006

Last reply on Sep 22, 2011 by Oldredbarn

I'll have to revisit the identification on this one. Originally the fore tarsal ratio made me think it's not Epeorus, but the unmarked wings, costal wing venation, and contiguous eyes now make me think otherwise.

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