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Range DescriptionThis species occurs in the USA from northern Del Norte and Siskiyou Counties, California, south through extreme western Trinity, Humboldt, and Mendocino Counties in an increasingly narrow, forested coastal strip to the vicinity of Stewart's Point, north-western Sonoma County, California. It is widespread on Vancouver Island and neighbouring islands in British Columbia, Canada, but reports from mainland British Columbia are unreliable. All Canadian populations might be derived from human-mediated introductions that occurred in conjunction with shipments of tan oak bark from California (Wake and Jackman, in Jackman 1998). The type locality in Humbold County is at 500m asl.