Western Slate Olive Duns

Mayflies

Caddisflies

Stoneflies

Scientific Names

Match	Scientific Name
	Drunella spinifera
	Drunella flavilinea

Like most common names, "Western Slate Olive Dun" can refer to more than one taxon. They're previewed below, along with 6 specimens. For more detail click through to the scientific names.

Mayfly Species Drunella spinifera

These are pretty much always called Western Slate Olive Duns.

This taxon prefers cold water and does not flourish where water temperatures exceed 60 degrees. As with the slightly larger Drunella coloradensis, this species prefers cold tailwaters, high elevation headwaters and spring creeks.

Male Drunella spinifera (Western Slate Olive Dun) Western Slate Olive Dun Nymph

Male Drunella spinifera (Western Slate Olive Dun) Mayfly Nymph

View 8 PicturesIn a bucket full of Drunella coloradensis nymphs, this was the only specimen of Drunella spinifera (and the first one I've found anywhere).

Collected July 28, 2019 from in
Added to Troutnut.com by on July 30, 2019

Female Drunella spinifera (Western Slate Olive Dun) Western Slate Olive Dun Dun

Female Drunella spinifera (Western Slate Olive Dun) Mayfly Dun

View 2 Pictures

Collected July 9, 2007 from in
Added to Troutnut.com by on June 29, 2011

Male Drunella spinifera (Western Slate Olive Dun) Western Slate Olive Dun Spinner

Male Drunella spinifera (Western Slate Olive Dun) Mayfly Spinner

View 2 Pictures

Collected July 9, 2007 from in
Added to Troutnut.com by on June 29, 2011

See 1 more specimens...

Mayfly Species Drunella flavilinea

These are very rarely called Western Slate Olive Duns.

The Flavs pick up about a week after the closely related but larger Western Green Drakes (Drunella grandis and Drunella doddsii) finish hatching on most Western waters.

Their hatches may be complemented by simultaneous hatches of two less prolific species, Drunella coloradensis and Drunella spinifera.

Drunella flavilinea (Flav) Mayfly Nymph

View 6 PicturesAlthough the identification is not certain because the nymph is not yet mature, the configuration of tubercles (

A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled. They are especially large in this species.

Tubercle: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.) on this one--particularly the forefemora--seems to best match Drunella flavilinea.

Collected July 2, 2019 from in
Added to Troutnut.com by on July 18, 2019

Female Drunella flavilinea (Flav) Mayfly Dun

View 6 PicturesI can't be certain of the ID of this female dun, but I'm calling it Drunella flavilinea for three reasons: 1) the known abundance of "flavs" on the Henry's Fork, 2) clear differences in coloration from my confirmed specimens of Drunella coloradensis, which is the main lookalike, and 3) the habitat (a sizable river in a wide mountain valley, rather than a small, high-altitude stream) suggests it's not coloradensis.

Collected July 31, 2020 from in
Added to Troutnut.com by on August 16, 2020

Drunella flavilinea (Flav) Mayfly Spinner

View 1 Pictures

Collected July 31, 2010 from in
Added to Troutnut.com by on June 29, 2011

Jargon Defined:

Dun: 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).

A few (not all) of the abdominal tubercles on this Ephemerella needhami nymph are circled. They are especially large in this species.

Tubercles: Various peculiar little bumps or projections on an insect. Their character is important for the identification of many kinds of insects, such as the nymphs of Ephemerellidae mayflies.