occurs (regularly, as a native taxon) in multiple nations

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Global Range: (20,000-2,500,000 square km (about 8000-1,000,000 square miles)) Range includes the Coast, Cascade, Rocky, and Sierra Nevada Mountains northward to Alaska and Yukon and southward to Mexico where it has been recorded disjunctly in Durango. It is found throughout the northern and eastern Basin and Range province of the western U.S. but is conspicuously absent in the western Great Basin, where P. princeps is the sole representative of the genus (Baumann et al., 1977; Kauwe et al., 2004; Sargent et al., 1991; Sheldon, 1979; Stark and Armitage, 2000; Stark et al., 1998; Stewart and Oswood, 2006; Stewart and Stark, 2002).

This is the very largest species of all mayflies, stoneflies, and caddisflies, up to 2.5 inches long. Range only overlaps with two other potentially confusing species; the American salmonfly, Pteronarcys dorsata, and the ebony salmonfly, Pteronarcys princeps. P. princeps is generally darker and typically found in small streams on the west coast primarily but also in isolated mountain ranges of Nevada, eastern Oregon, and southwestern British Columbia. The tenth sternum (= ventral plate; essentially the very last segment) is greatly narrowed ventrally (as opposed to broad like in most species or absent in P. dorsata and P. pictetii). P. dorsata resembles P. californica in coloration but the ninth abdominal sternum (= ventral plate) of males projects over the tenth and is notched on the posterior margin (making the tenth plate appear absent); plus it only gets as far west in the Rocky Mountains as the Mississippi-Missouri drainage basin. In adults, the tenth abdominal tergum (= dorsal plate on the last segment) is rounded with raised lobes (unlike P. dorsata which is not raised) projecting about as high as their width unlike P. princeps where the lobes are plate-like (not rounded) and project higher than the width. In females, the posteromesal processes of the subgenital plate (= projections extending from the tail) are produced backward (unlike P. dorsata where they are reduced) and are about as long as they are wide at their base (unlike P. princeps where they are longer).

In mature nymphs, the prothoracic (= corner) teeth are directed outward and are sharp and longer than their basal width (unlike P. dorsata and P. princeps whose corner teeth are blunt and short and no longer than their basal width).

Habitat Type: Freshwater

Comments: Adults and larvae are associated with fast-moving mountain streams or large to medium sized rivers (2nd to 7th order streams) at relatively low to moderate elevations (Schwiebert, 2007; Stark et al., 1998). Streams are often clean and of moderate to high velocity and nymphs are frequently found in medium to large-sized, unconsolidated rocky substrates (Elder and Gaufin, 1973; Kauwe et al., 2004).

Non-Migrant: No. All populations of this species make significant seasonal migrations.

Locally Migrant: No. No populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Comments: Gut content was found to be 75% diatoms, 15% vascular plant material, and 8% animal remains (Freilich, 1991).

Note: For many non-migratory species, occurrences are roughly equivalent to populations.

Estimated Number of Occurrences: > 300

Comments: Gaufin et al. (1972) cite Montana distribution as Beaverhead (Big Hole River), Flathead (Camas Creek, Kintla Creek, Swan River), Gallatin (Gallatin River, Madison River, West Gallatin River), Glacier (Elizabeth Creek), Granite (Flint Creek, Gilbert Creek, Rock Creek, Stony Creek), Lake (Swan River), Lewis and Clark (Prickley Pear Creek), Lincoln (Fisher River), Madison (Madison River, Spring Creek), Missoula (Blackfoot River, Lolo River, Rock Creek), Park (Yellowstone River), Ravalli (Bitterroot River, East Fork Bitterroot River, Cameron Creek, Camp Creek), and Sweet Grass (Boulder River) Cos. Baumann (1973) recorded it from Utah. Branham and Hathaway (1975) conducted a growth study on a population in the Provo River, Utah. Call and Baumann (2002) cite southern Utah distribution as Beaver Valley, Pine Valley Mountains, Sevier Plateau, Tushar Mountains, Wasatch Plateau, and Capitol Reef. Newell et al. (2006) report it from Glacier National Park in western Montana. Rockwell and Newell (2009) studied mortality in a population on the Jocko River, Montana. Gregory et al. (2000) documented emergence in streams in the Henry's Fork catchment, Idaho. In California, Jewett (1960) cited Butte, Kern, Marin, Mendocino, Placer, Plumas, San Mateo, Santa Clara, Sonoma, and Stanislaus Cos. Kauwe et al. (2004), in an analysis of global phylogeography, examined specimens from California (Lake, Mendocino, Shasta, Siskiyou Cos.), Idaho (Clark, Custer, Elmore, Fremont, Valley Cos.), Nelson and Hanson (1971) documented specimens from California, Colorado, Idaho, Montana, New Mexico, Oregon, Utah, Wyoming, and the Yukon. Montana (Madison, Park Cos.), Nevada (Elko Co.), New Mexico (San Miguel Co.), Oregon (Benton, Grant, Jackson Cos.), Utah (Beaver, Cache, Emory, Garfield, Utah, Weber Cos.), Washington (Walla Walla Co.), and Wyoming (Lincoln, Park, Pine Dale, Sheridan Cos.). Stewart and Ricker (1997) report the species from the Yukon for the first time from Klusha Creek on the Klondike Highway. Townsend and Pritchard (1998) documented it in the Crowsnest River in southern Alberta.

This species has a semivoltine (2-, 3-, or rarely 4-year) life cycle including a 9-11 month diapause (Branham and Hathaway, 1975; DeWalt and Stewart, 1995; Freilich, 1991; Gaufin et al., 1972; Stewart and Stark, 2002). After three years in the water, mature nymphs emerge along the shoreline but emergence is earlier with higher water temperature (Gregory et al., 2000). Small scale migration is heaviest near dawn and dusk. Adults are present in Alaska and western Canada mostly in May and June (Stewart and Oswood, 2006). Emergence time in the contiguous states is generally April to June (Stark et al., 1998), mid- to late May to as late as mid-June in eastern Idaho depending on water temperature (Gregory et al., 2000), early April through early May in northwestern Montana (Rockwell and Newell, 2009), and throughout May in southern Alberta (Townsend and Pritchard, 1998). It is on the wing in western mountains during June, July, and August (Needham and Claasen, 1925).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 15
Species With Barcodes: 1

Canada

Rounded National Status Rank: N4 - Apparently Secure

United States

Rounded National Status Rank: N5 - Secure

Rounded Global Status Rank: G5 - Secure

Reasons: Range includes the Coast, Cascade, Rocky, and Sierra Nevada Mountains northward to Alaska and Yukon.

Environmental Specificity: Narrow. Specialist or community with key requirements common.

Comments: Rockwell and Newell (2009) documented mortality due to cold air temperature following early emergence on the Jocko River in Montana.

Comments: Rockwell and Newell (2009) documented mortality due to cold air temperature following early emergence on the Jocko River in Montana.

Comments: An analysis of gene sequences from populations across North America revealed an eastern North American origin and 2 distinct genetic lineages with most of the current population structure in both lineages explained by a pattern of restricted gene flow with isolation by distance (presumably the result of dispersal via connected streams and rivers), but also some long-distance, overland dispersal (Kauwe et al., 2004).