The giant Salmonflies of the Western mountains are legendary for their proclivity to elicit consistent dry-fly action and ferocious strikes.
In 46 records from GBIF, adults of this species have mostly been collected during June (57%), July (26%), May (9%), and August (7%).
In 8 records from GBIF, this species has been collected at elevations ranging from 341 to 2723 ft, with an average (median) of 1951 ft.
Time of day: Late evening to dusk, sometimes later
Habitat: Riffles, possibly elsewhere
Current speed: Slow to medium
Substrate: Silt or sand and gravel
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 rather pale species; fore wing tinged with brownish except in anal region, hind wing pale; no dark blotch in apical third of wing beyond bullar stripe.
Frontal portion of head reddish, carina black; basal antennal segments black apically, filament brownish, tips pale. Vertex red-brown, blackish between and at bases of ocelli. Thoracic notum light red-brown. A wide blackish longitudinal stripe on each side of pronotum. Mesonotal scutellum pale; dark brown area anterior to this; middle portion of mesonotum paler yellowish, also a pale median line; anterolateral margins brown. Metanotum pale, with transverse dark band near center. Pleura yellowish; red-brown oblique streak before middle and hind leg. Sternum pale yellowish, anterior portion of mesosternum marked with brown. Coxa and trochanter of fore leg yellowish; femur rather olive brown, yellowish at base, apex darker; base and apex of tibia widely brown, remainder yellowish, apical half brown-tinged; tarsus yellowish brown, short basal joint, apical half of distal joint and all joinings, dark brown. Middle and hind legs creamy white, claws faintly tinged with brownish.
Wings hyaline; fore wing tinged with brownish except in anal region and near base, where wing membrane and veins are pale or colorless; stigmatic area most deeply tinged. Longitudinal veins yellowish to yellow-brown. Cross veins blackish, those of basal costal and subcostal spaces margined narrowly with dark brown, many in the disc with wider marginings. A wide dark purplish band at bulla, slightly curved, and extending backward as far as space above anterior branch of media, wide enough to cover three cross veins. Posterior to this and nearer the margin, a smaller dark purple cloud; another at basal end of long intercalary of media. No cloud in apical third of wing beyond bullar stripe, though a few cross veins in third space are margined. Hind wing pale; costa and subcosta yellowish, basal cross veins in these spaces pale purplish; all other veins colorless, none dark-margined. Outer margin may be faintly yellow.
Abdominal tergites largely purplish grey; lateral margins, postero-lateral angles and mid-dorsal area pale yellowish white. On tergites 2-9, a pair of purplish black oblique submedian streaks extend backward and laterad from anterior margin on each side, conjoined posteriorly; inner of these not extending beyond middle of tergite, outer a little longer. Between these and along outer margin, whitish spaces. Blackish markings along pleura much as in Ephemera blanda. Posterior margins of tergites, and middle portion of sternites, dark purplish. Sternites pale yellowish white. A black longitudinal streak on each side, and a dark mid-ventral streak on sternites 8 and 9, as in Ephemera blanda. Forceps base yellowish brown, forceps yellowish; second joint longer than in Ephemera simulans; penes rather narrower (fig. 82). Tails yellowish to greyish yellow, joinings dark brown.
The darker abdominal tergites and more extensive blotches in fore wing distinguish this species from the allied Ephemera blanda. Venter of abdomen paler, wings less extensively dark-margined, body paler than Ephemera simulans. Nymph shown in fig. 80.