Status Review of Three Formerly Common Species of Bumble Bee ...

Pedicularis capitata, P. kanei, and P. langsdorfii (Macior 1978a), Pedicularisgroenlandica (Macior 1968b), Penstemon procerus (Bauer 1983), Phacelia spp. (Thorpet al. 1983), Prunus spp. (Macfarlane and Patten 1997), Raphanus spp. (Thorp et al.1983), Rhododendron spp. (Thorp et al. 1983), Salix spp. (Macfarlane and Patten 1997),Salvia spp. (Thorp et al. 1983), Solidago spp. (Thorp et al. 1983), Symphoricarpos spp.(Thorp et al. 1983), Tanacetum spp. (Thorp et al. 1983), Taraxacum spp. (Thorp et al.1983), Trifolium dasyphyllum (Bauer 1983), Trichostema spp. (Thorp et al. 1983),Trifolium spp. (Thorp et al. 1983), and Zea spp. (Thorp et al. 1983).C. Population Distribution and StatusAccording to Milliron (1971), the historic range of B. occidentalis was the west coast ofNorth America from central California north to Alaska, east through Alberta and westernSouth Dakota, and southward into Arizona and New Mexico (see Figure 7). U.S. statesincluded in B. occidentalis’ historic range are northern California, Oregon, Washington,Alaska, Idaho, Montana, western Nebraska, western North Dakota, western SouthDakota, Wyoming, Utah, Colorado, northern Arizona, and New Mexico. Canadianprovinces included in its historic range are Alberta, British Columbia, Saskatchewan, andthe Yukon Territory. B. occidentalis was considered abundant in California (Thorp et al.1983) and in the Pacific Northwest (Stephen 1957). See Appendix IC for a list of some ofthe B. occidentalis records from major museum collections.Figure 7. Historic distribution of Bombus occidentalis. Map is based on Milliron (1971).In 2007, James Strange and his colleagues visited many historical B. occidentalis sites.They found B. occidentalis at approximately one quarter of the historical sites that werevisited, including sites in Utah, northeastern California, southern Oregon, and Nevada (J.Strange, personal communication September, 2007; see Figure 8).Since 1998, B. occidentalis has declined most dramatically from western and centralCalifornia, western Oregon, western Washington, and British Columbia. Although absentfrom much of its former range, B. occidentalis is still found in isolated areas, primarily in19