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Artistic view of a Male Pteronarcys californica (Pteronarcyidae) (Giant Salmonfly) Stonefly Adult from the Gallatin River in Montana
Pteronarcys californica

The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.

Dorsal view of a Setvena wahkeena (Perlodidae) (Wahkeena Springfly) Stonefly Nymph from Mystery Creek #199 in Washington
As far as I can tell, this species has only previously been reported from one site in Oregon along the Columbia gorge. However, the key characteristics are fairly unmistakable in all except for one minor detail:
— 4 small yellow spots on frons visible in photos
— Narrow occipital spinule row curves forward (but doesn’t quite meet on stem of ecdysial suture, as it's supposed to in this species)
— Short spinules on anterior margin of front legs
— Short rposterior row of blunt spinules on abdominal tergae, rather than elongated spinules dorsally
I caught several of these mature nymphs in the fishless, tiny headwaters of a creek high in the Wenatchee Mountains.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Species Drunella flavilinea (Flavs)

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

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.

In 4 records from GBIF, adults of this species have been collected during June (100%).

Species Range

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.


To determine whether a specimen of Drunella belongs to Drunella flavilinea, use the Key to Species of Drunella Nymphs.

Physical description

Most physical descriptions on Troutnut are direct or slightly edited quotes from the original scientific sources describing or updating the species, although there may be errors in copying them to this website. Such descriptions aren't always definitive, because species often turn out to be more variable than the original describers observed. In some cases, only a single specimen was described! However, they are useful starting points.

Male Spinner

Described in Needham et al (1935) as Ephemerella flavilinea

A species of the fuscata group (now a synonym of Drunella walkeri); very close to E. coloradensis (now a synonym of Drunella coloradensis. The imago is distinguished from the latter species by the pale venation, and rather sharp constriction of the second joint of the forceps, near the apex.

Head and thorax deep ruddy brown. Femur and tibia of fore leg deep blackish brown; tarsi dull whitish. Tibia once and a half as long as the femur, and slightly shorter than the tarsus. Middle and hind legs are dull yellowish; a reddish brown apical patch on each femur on the inner side. Wings hyaline, venation pale. Abdominal tergites deep ruddy brown; sternites more reddish than the dorsal surface. A pale yellowish line along the pleural fold, which tends to extend upward at the edge of each segment, especially on the posterior ones. Tails blackish at the base, paler toward the tips. Second joint of the forceps with a rather sharp constriction near the apex; the tip bent inward (see fig. 153).


Described in Needham et al (1935) as Ephemerella flavilinae

Nymph without frontal horns or a frontal shelf (see fig. 151 d). Occipital tubercles present, but no thoracic spines. Anterior margin of the fore femur with teeth or spines. Dorsal abdominal spines present on 2-9; very small on 9; somewhat shorter than in coloradensis (now a synonym of Drunella coloradensis). Tibial ‘thumb’ shorter than in coloradensis; fore tibia more slender; middle and hind legs stouter. General color variable, ranging from light to dark brown; pale specimens appear distinctly mottled. Femora with three pale indistinct areas; tibiae with distinct pale bands at each end; tarsi banded in the middle. Tails pale; narrow blackish bands beyond the middle and at the tips.

Specimens of the Mayfly Species Drunella flavilinea

1 Male Dun
1 Female Dun
1 Male Spinner
2 Nymphs

Start a Discussion of Drunella flavilinea


Mayfly Species Drunella flavilinea (Flavs)

Species Range
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