Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: > 300
Comments: This species has recently been reported from several sites in New Hampshire (Chandler et al., 2006). In Washington, it occurs in Stevens, Skamania, Thurston, Asotin, Clallam, Columbia, Douglas, Grant, Jefferson, Kitsap, King, Kittitas, Lewis, Pierce, Skagit, Snohomish, Spokane, Whitman, Yakima, Cowlitz, Wahkiakum, Benton, Chelan, Ferry, Franklin, Garfield, Grays Harbor, Klickitat, Lincoln, Mason, Okanogan, Pacific, Oreille, Skamania, snoomish, Stevens, Thurston, Union, Walla Walla, Whatcom Cos. (Meyer and McCafferty, 2007). In Oregon, it occurs in Baker, Benton, Clackamas, Clatsop, Columbia, Coos, Crook, Curry, Deschutes, Douglas, Gilliam, Grant, Harney, Hood River, Jackson, Jefferson, Josephine, Klamath, Lake, Lane, Lincoln, Linn, Malheur, Marion, Morrow, Multnomah, Polk, Sherman, Tillamook, Umatilla, Union, Willowa, Wasco, Washington, Wheeler, and Yamhill Cos. (Meyer and McCafferty, 2007). This species has been documented in Yellowstone National Park, Wyoming (McCafferty, 2007). In South Dakota, it occurs in Butte, Custer, Deuel, Fall River, Grant, Lawrence, Meade, Pennington, and Roberts Cos. (Guenther and McCafferty, 2008). It was recently documented in the Humboldt River (just below the confluence of the North Fork), Nevada (Baumann and Kondratieff, 2000). In South Carolina, it occurs in Greenville, Kershaw, Oconee, and Pickens Cos. (McCafferty and Meyer, 2008). McCafferty et al. (2008) cite records from Marin and Sonoma Cos., California (originally misidentified as B. alius). It is also known from the Ruckee River at Reno, Nevada (as Baetis parallelus) (McCafferty, 2007). Meyer and McCafferty (2008) documented California occurrences in Alameda, Alpine, Amador, Butte, Calaveras, Calusa, Contra Costa, Del Norte, El Dorado, Fresno, Glenn, Humboldt, Inyo, Kern, Lake, Los Angeles, Madera, Marin, Mariposa, Mendocino, Merced, Modoc, Mono, Monterey, Napa, Nevada, Placer, Plumas, Riverside, Sacramento, San Benito, San Bernardino, San Diego, San Joaquin, San Luis Obispo. San Mateo, Santa Barbara, Santa Clara, Shasta, Sierra, Siskiyou, Sonoma, Stanislaus, Sutter, Tehama, Trinity, Tulare, Tuolumne, Ventura, Yolo, and Yuba Cos. Whiting (1992) cites occurrences in Nova Scotia in Inverness and Antigonish Cos.