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**Mayfly Species Drunella flavilinea (Flav)**

Mayflies

Caddisflies

Stoneflies

Taxonomic Navigation -?-

Kingdom Animalia (Animals)

» Phylum Arthropoda (Arthropods)

» Class Insecta (Insects)

» Order Ephemeroptera (Mayflies)

» Family Ephemerellidae (Hendricksons, Sulphurs, PMDs, BWOs)

» Genus Drunella (Blue-Winged Olives)

» Species flavilinea (Flav)

Common Names

Match	Common Name
	Flav
	Small Western Green Drake
	Dark Slate-Winged Olive
	Western Slate Olive Dun
	Western Slate Olive
	Western Green Drake
	Dark Olive Spinner
	Slate-Winged Olive
	Blue-Winged Olive

Pictures Below ↓

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.

Where & When

Region: West

Time Of Year (?): July and August

Altitude: 4000-6000 Feet

They are reported in places from mid-June all the way through October, but they peak in most places sometime in July or August.

Hatching Behavior

Time Of Day (?): Flexible, but usually in the evening

Habitat: Quiet water adjacent to the fast-water nymphal habitat

Water Temperature: 55-57°F

According to Knopp & Cormier in Mayflies: An Angler's Study of Trout Water Ephemeroptera , Flavs emerge in the surface film rather than underwater like most other Drunella mayflies.

The Flav duns don't have as much difficult getting off the water as their larger brethren, but they still linger longer as duns than most mayflies and provide good dry fly action.

Spinner Behavior

Time Of Day: Late morning, or evening

Habitat: Riffles

In Hatches II, Caucci and Nastasi say the spinner falls occur in the evenings. However, in Selective Trout, Swisher and Richards say that most of the spinners fall between 9am and 1pm and a few fall in the evening. Anglers with experience to clarify this contradiction are encouraged to write their observations in the comments.

Nymph Biology

The nymphs occur in many habitats but they're most prolific in fast, rocky water.

Pictures of 3 Mayfly Specimens in the Species Drunella flavilinea:

Drunella flavilinea (Flav) Mayfly Spinner

View 1 Pictures

Collected July 31, 2010 from the Flathead River-lower in Montana
Added to Troutnut.com by Bnewell on June 29, 2011

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 the Gallatin River in Montana
Added to Troutnut.com by Troutnut 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 the Henry's Fork of the Snake River in Idaho
Added to Troutnut.com by Troutnut on August 16, 2020

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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.

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).

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.

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.

Useful References:

Arbona, Fred Jr. 1989. Mayflies, the Angler, and the Trout. Nick Lyons Books.

Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.

Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.

Swisher, Doug and Carl Richards. 2000. Selective Trout. The Lyons Press.