The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
...the male only exhibits this coloration on segments eight to ten, against an otherwise whitish to translucent body.
In 5 records from GBIF, adults of this species have been collected during July (80%) and June (20%).
Current speed: Fast
Substrate: Gravel and rock
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.
A species of Stenonema pulchellum group; thorax almost wholly deep black brown; spiracular dots usually present; tails not, darker at joinings.
Frontal portion of head pale whitish; vertex sepia brown with ruddy shading next to the eyes. Thorax, dorsally and ventrally, deep black brown, except a whitish patch on pleura anterior to wing roots and slight paler shading below wing roots. Posterior portion of scutellum with faint paler shading; a small whitish median dot anterior to scutellum, and two small white lateral streaks. Legs whitish; median and apical purplish bands on femora; fore tarsus black-tipped at apex; basal joint of fore tarsus more than half as long as second. Wings hyaline; veins fine, black, cross veins in costo-apical region slightly thickened.
Abdominal segments 2-7 hyaline white; scarcely a trace of darker posterior margins, only a small dark transverse dash on posterior margin of each, at mid-dorsal line. Black spiracular dots present on segments 4-7 (may be obsolete). Segments 8-10 opaque, whitish; tergite 8 in posterior half, and all of 9, shaded with light sepia brown. Forceps whitish; genitalia of the pulchellum type(?). Tails wholly white, not darker at joinings.
The very dark thorax, short dark median dash on tergites and fine veins distinguish this species from its near allies.
Described as S. nepotellum subspecies mediopunctatum
Body length 8 mm, wing length 8-10 mm
A species of the Stenonema pulchellum group; spiracular dots present; tails dark-ringed; reddish stain in stigmatic area of fore wing.
Head very similar to S. rubromaculatum (now a synonym of Stenonema modestum). Mesonotum ochre-brown; anterolateral margins narrowly whitish. Scutellum whitish, also lateral margins to base of fore wing. Metanotum largely ochre-brown; median elevation whitish. Pleura yellowish-white, with brown shading as in rubromaculatum; anterior to wing roots shaded with light reddish. Legs very much as in rubromaculatum; posterior margin of fore coxa narrowly black; less reddish shading laterally than in that species; purplish bands on femora also less distinct, may be wanting on hind leg. Wings as in rubromaculatum.
Abdominal segments 1-7 hyaline, pale yellowish white; posterior margins of tergites somewhat more distinctly black than in rubromaculatum; black spiracular dots well defined. Segments 8-10 opaque white; tergites largely suffused with pinkish brown; on anterior margin of 8, slight pale submedian wedge-shaped marks; posterior margin of 10 also white. Genitalia of rubromaculatum type. Tails pale; joinings narrowly brown.
In the imago stage, this species is very close to S. rubromaculatum and S. annexum (now a synonym of Stenonema modestum); may be distinguished as indicated under those species. Ventral markings of nymph are distinct from either of these, and very similar likewise to Stenonema ithaca.