Note: For many non-migratory species, occurrences are roughly equivalent to populations.
Estimated Number of Occurrences: > 300
Comments: This species was first recorded in Hawaii in 1897 (Cowie, 1997) but has probably become established on all main Hawaiian Islands, inclduing Lanai, Kauai, Oahu, and Maui. Recently it was found in a survey of the Hakalau region, dry gulch near University of Hawaii Hakalau Forest Biological Field Station, Hakalua Forest National Wildlife Refuge, on the windward slopes of Mauna Kea, elevation 6335-6410 feet, Hawaii, Hawaiian Islands (Howarth et al., 2003). Roth and Lindberg (1981) documented it on Attu (Aleutian Islands), Alaska. In California it is known from 14 counties: Alameda, Lake, Los Angeles (including Santa Catalina Island), Marin, Nevada, Placer, Shasta, San Bernardino, San Diego, San Francisco, San Mateo, Santa Barbara (including Santa Cruz Island), Santa Cruz (Roth and Sadeghian, 2006), and Humboldt (McDonnell et al., 2009). It had been documented historically in Colorado (Cockerell, 1927) as Agriolimax campestris. Multiple species of Deroceras spp. were recorded in eastern Maine (11 of 101 sites) from litter samples in a variety of habitats (Nekola, 2008). In New York, Hotopp and Pearce (2007) report it from four counties that are widespread, though it is likely poorly represented. It has been documented recently in southeastern Wisconsin (Jass, 2006). This species is also known from Pleistocene deposits in the Black Hills of Fall River/Custer Cos., South Dakota (Jass et al., 2002). Freeman and Perkins (1992) documented it in Nebraska along the entire Platte River valley. Branson (1966) includes a single site on the Spring River in Missouri. Baxter (1987) cites occurrences in Alaska across much of the state. In Alberta, it is distributed south west of Calgary, north to Lake Louise and Jasper, east to Edmonton and north to Slave Lake (Lepitzki, 2001). It was recently documented in 2 of 82 soil samples and 6 area spot searches of Wind Cave National Park, South Dakota, in 2002 (Anderson, 2005). Pearce (1994) reported it from Mackinac Island, Michigan. Forsyth (2005) documented it in the Upper Fraser Basin of central British Columbia along the shorelines of waterways and permanently wet forested sites; as well as in the Peace-River- northern Rockies region in a small pond west of Ed Bird Lake in the Finlay River valley and in spruce and mixedwood forests such as those on the Liard Plain (Forsyth, 2005). Most recently, it was discovered in the Ktunaxa Traditional Territory in southeastern British Columbia (which extends from near Canada - U.S. border north to about 50 km north of Cranbrook) (Ovaska and Sopuck, 2009).