SPECIES FACT SHEET

Scientific Name: Bombus occidentalis Greene, 1858 Common Name: Western bumble bee Phylum: MandibulataClass: InsectaOrder: HymenopteraFamily: ApidaeTribe: BombiniGenus: BombusSubgenus: Bombus sensu stricto Latreille(ITIS 2020)

Conservation Status: Global Status: G4 – Apparently Secure (last reviewed 8 April 2018)  National Statuses (United States): N2N3State Status: S1S2 (Oregon); S2S3 (Washington) (NatureServe 2020) Federal Status (United States): Under Review (USFWS 2020) IUCN Red List: Vulnerable (Hatfield et al. 2015)

Synonyms: Bombus howardi Cresson, 1863; B. proximus Cresson, 1863; B. howardii Cresson, 1879; B. perixanthus Cockerell and Porter, 1899; B. proximus coloradensis Titus, 1902; B. occidentalis nigroscutatus Franklin, 1912; B. terricola severini Frison, 1926; Bremus terricola severini Frison, 1926

Taxonomic Note: Bombus occidentalis is considered a valid species (Franklin 1913, Thorp and Shepherd 2005, Cameron et al. 2007, Bertsch et al. 2010, Williams et al. 2012, Owen and Whidden 2013). However, a recent analysis of mitochondrial DNA by Williams et al. (2012) suggests that B. occidentalis can be divided into northern (including Alaska and northern British Columbia) and southern (including the western contiguous United States and southern British Columbia) populations, each of which have distinctive haplotype groups. These distinct haplotypes correspond with morphological differences; shorter pile (hair) has been noted in the southern populations and longer pile in the northern populations (Williams et al. 2012). More recent taxonomic work formally distinguished two subspecies of B. occidentalis (Sheffield et al. 2016). B. o. mckayi is principally found north of 55° N, with B. o. occidentalis

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found south of 55° N. All individuals in Oregon and Washington are B. o. occidentalis.

Technical Description: Bumble bees (Tribe Bombini, Genus Bombus) are large-bodied insects ranging in size from 9mm to 22 mm, bombiform in shape, and generally covered in dense hairs that are black, orange, yellow or white (Michener 2000, Thorp et al. 1983). They can be distinguished from other large-bodied bees in the Anthophorini or Eucerini tribes by the long cheeks (malar spaces) on the face and pollen baskets (corbicula) on the hind tibiae of females (Michener 2000). Carpenter bees (Tribe Xylocopini, Genus Xylocopa) are often mistaken for bumble bees, although most carpenter bees have shiny abdomens and are fitted with dense pollen-collecting hairs (scopae) on the hind leg rather than the hairless, pollen baskets that bumble bees possess. Carpenter bees are rare in the Pacific Northwest; records from Oregon are largely confined to Jackson, Josephine, Klamath, Lane and Wallowa counties, and they do not occur in Washington, though observations have been made in Idaho and British Columbia (Discover Life 2020).

Bombus occidentalis is most easily distinguished from other Bombus species based on hair coloration. Note, however, that coloration in this species can be highly variable (Thorp et al. 1983) and a total of twelve female and twelve male color forms have been described (Franklin 1913). The color forms of B. occidentalis that are most likely to be encountered in Oregon and Washington have bright white coloration on the posterior end of the abdomen (R. Thorp pers. comm. May 2013); this character is unusual and obvious. The nominate form, which is one of the primary color forms found in Oregon and Washington (Xerces Society 2012), is illustrated in Attachment 4 and described by Evans et al. 2008 as follows:

Queens and Workers: Bombus occidentalis queens and workers are similar in coloration. The queen is 17 to 19 mm in length, 9 to 10 mm in breadth. The worker is 9 to 14 mm in length, 5 to 7 mm in breadth. Their hair is entirely black on the head. Their hair is yellow on the front part of the thorax. The first through the basal section of the fourth abdominal segments have black hair. The apex of the fourth abdominal segment as well as segments five and six are whitish. The hair on their legs is black.

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Males: The male is 13 to 17 mm in length, 6 to 8 mm in breadth. The hair on the head is pale yellowish on the front of the face. The top of the head has pale yellowish hairs medially, with some black hairs, especially laterally. The hair on the front of the thorax is pale yellowish. The hair on the first to third abdominal segments is black. The basal part of the fourth abdominal segment is black, with the remainder, as well as segments five to seven, whitish.

Koch et al. (2012) describe additional useful characters of all color forms of female B. occidentalis as follows:

Face round. Mid leg basitarsus with the distal posterior corner rounded. Cheek length slightly shorter than width… On the side of the thorax, the lower anterior surface with predominantly black hair, sometimes with yellow intermixed, corbicular fringes red. Hair length medium and even.

Life History: Bumble bees are primitively eusocial insects that live in colonies made up of one queen, female workers, and, near the end of the season, reproductive members of the colony (new queens, or gynes, and males). New colonies are initiated by solitary queens, generally in the early spring. This process includes locating a suitable nest site; collecting pollen and nectar from flowers; building a wax structure to store nectar; forming a mass of pollen to lay eggs on; and building a wax structure to enclose the eggs and pollen. Bombus occidentalis, like most other species of bumble bees, primarily nests underground in abandoned rodent burrows or other cavities (Hobbs 1968, MacFarlane et al. 1994, Plath 1922, Thorp et al. 1983). Thus, B. occidentalis nesting sites may be limited by rodent abundance (Evans et al. 2008).

Once the colony has been initiated by the queen and the first brood of female workers have grown, pupated, and emerged as adults, the female workers take over all duties of foraging for pollen and nectar, colony defense, and feeding larvae. The queen’s only responsibility at this point is to lay eggs. Bombus occidentalis colonies can contain as many as 1,685 workers and produce up to 360 new queens; this colony size is considered large relative to many other species of bumble bees (MacFarlane et al. 1994).

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Bumble bees, including B. occidentalis, are generalist foragers and have been reported visiting a wide variety of flowering plants. Bombus occidentalis has a short tongue, and thus is best suited to forage on open flowers with short corollas. In addition to foraging at the open face of flowers, B. occidentalis is also known to engage in a behavior called ‘nectar robbing’ in which a hole is chewed in the base of flowers with long corollas to obtain nectar without actually facilitating plant pollination.

According to Thorp et al. (1983), the flight period for B. occidentalis queens in California is from early February to late November, peaking in late June and late September. The flight period for workers and males in California is from early April to early November; worker abundance peaks in early August, and male abundance peaks in early September (Thorp et al. 1983). Graves et al. (2020) found that peak detection rates for B. occidentalis occur in mid-July throughout its range in the contiguous United States.

In the late summer or fall, depending on the bumble bee species and elevation, colonies produce reproductive individuals (males and gynes), which leave the colony and mate. As winter approaches, the old queen, workers, and males die, while the gynes continue to forage for nectar, then find a suitable location (hibernacula), usually burrowed a few centimeters underground, in which to spend the winter. The newly mated queens store sperm until they initiate a colony the following spring.

Bumble bees may be more vulnerable to extinction than other species due to their unique system of reproduction (haplodiploidy with single locus complementary sex determination) (Zayed and Packer 2005, reviewed in Zayed 2009). Range, Distribution, and Abundance: Type Locality: North West coast of America, Fort Vancouver, Dr. Cooper; Puget’s Sound, Dr. Suckley (Greene 1858)

Range: Bombus occidentalis was historically broadly distributed across the west coast of North America from Alaska to central California, east through Alberta and western South Dakota, and south to Arizona and New Mexico (Williams et al. 2014). A rangewide analysis including more than 73,000 records of eight bumble bee species suggests that B. occidentalis has undergone a 28% range decline between recent (2007-2009) and historic (1900-1999) time periods (Cameron et al. 2011a). A separate, unpublished

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analysis comparing the current (2002-2012) and historic (1805-2001) ranges of B. occidentalis (using a database of more than 200,000 records of 43 species of North American bumble bees developed by Williams et al. 2014) suggests that this species has declined from 50% of its historic range; the southern subspecies (B. o. occidentalis) has been lost from 62% of its historic range (Hatfield et al., unpublished data). The relative abundance of B. occidentalis has declined by 75% (Hatfield et al., unpublished data). Declines are most significant at the edges of this species’ range (Hatfield et al., unpublished data). In Oregon and Washington, B. occidentalis populations are currently largely restricted to high elevation sites (Xerces Society et al. 2020), east of the Cascade Crest; the species is rarely found in the western portions of either state where it was once common (Cameron et al. 2011a, Xerces Society et al. 2020).

Distribution:

BLM/Forest Service Land: Documented: In Washington, Bombus occidentalis has been Documented on Colville, Gifford Pinchot, Mt. Baker-Snoqualmie, Okanogan-Wenatchee, and Olympic National Forests, and BLM land in the Spokane District. In Oregon, this species has been Documented on Deschutes, Fremont-Winema, Klamath, Malheur, Mt. Hood, Ochoco, Rogue River-Siskiyou, Siuslaw, Umatilla, Umpqua, Wallow-Whitman, and Willamette National Forests, and BLM land in the Burns, Lakeview, and Medford Districts.

Given the relatively recent range contraction for this species, it is unknown what the current “Documented” status is for many of these field units, as many of the documented sites are considered historic. The Oregon Biodiversity Information Center (ORBIC 2019) lists documented sites for this species as occurring in Baker, Clackamas, Coos, Deschutes, Douglas, Gilliam, Hood River, Jackson, Jefferson, Josephine, Klamath, Lake, Lane, Lincoln, Polk(?), Union, and Wallowa Counties, although a recent compilation of records in support of this fact sheet also includes Benton, Clatsop, Columbia, Crook, Curry, Grant, Harney, Linn, Malheur, Marion, Multnomah, Umatilla, Wasco, Washington, Wheeler, and Yamhill Counties (Xerces Society 2020).

Suspected: It is Suspected on BLM land in the Northwest Oregon, Prineville, and Vale Districts based on close proximity to known records.

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Abundance: Since most historic records available for B. occidentalis are from incidental observations or museum specimen records rather than from quantitative studies, population estimates at specific sites are largely unavailable. Furthermore, using field estimates of abundance to understand bumble bee population stability can be problematic because observations of multiple individuals may represent a single reproductive unit (because of the colonial life history of bumble bees). Recent efforts (2018-2020) in Oregon and Washington, including the Pacific Northwest Bumble Bee Atlas (PNWBBA), have conducted equal effort surveys that provide baseline data to which future efforts can be compared (Xerces Society et al. 2020). The PNWBBA survey protocol is available online (Xerces Society et al. 2018).

Relative abundance can be a useful metric to evaluate population trends in bumble bee species. In a database of more than 200,000 records of North American bumble bees, B. occidentalis specimens comprised approximately 1.6% of all North American bumble bee records from 2002-2012, whereas B. occidentalis comprised approximately 6.3% of all records from 1801-2002 (Hatfield et al., unpublished data).

The relative abundance of B. occidentalis in Oregon and Washington in all years prior to the PNWBBA was 9.8% (pre-2018, 24,822 total records) (Data analysis from Richardson 2019). During the PNWBBA (2018-2020) the relative abundance of B. occidentalis in OR and WA was 1.65% (total records 15,108) (Xerces Society et al. 2020).

A recent study, based on data up to 2018, found that the probability of local occupancy of B. occidentalis has declined by 93% over the last 20 years (Graves et al. 2020). Likewise, a recent study found that the relative abundance of B. occidentalis in Washington state declined from 27% (pre-1990) to <0.1% (1990-2015).

Habitat Associations: Bumble bees inhabit a wide variety of natural, agricultural, urban, and rural habitats, although species richness tends to peak in flower-rich meadows of forests and subalpine zones (Goulson 2010). While B. occidentalis was historically known throughout Oregon and Washington, it is now largely confined to high elevation sites and areas east of the Cascade Crest (Williams et al. 2014, Cameron et al. 2011, Xerces Society et al. 2020).

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Like other bumble bees, Bombus occidentalis has three basic habitat requirements: suitable nesting sites for the colonies, nectar and pollen from diverse floral resources available throughout the duration of the colony period (spring, summer and fall), and suitable overwintering sites for the queens.

Nest Sites: Reports of B. occidentalis nests are primarily in underground cavities such as old squirrel or other animal nests and in open west-southwest slopes bordered by trees, although a few nests have been reported from above-ground locations such as in logs among railroad ties (Plath 1922, Hobbs 1968, Thorp et al. 1983, MacFarlane et al. 1994). Availability of nest sites for B. occidentalis may depend on rodent abundance (Evans et al. 2008). Nest tunnels have been reported to be up to 2.1 m long for this species and the nests may be lined with grass or bird feathers (MacFarlane et al. 1994).

Floral Resources: Bumble bees require plants that bloom and provide adequate nectar and pollen throughout the colony’s life cycle, which is from early February to late November for B. occidentalis (although the actual dates likely vary by elevation). The amount of pollen available to foragers directly affects the number of new queens that a bumble bee colony can produce, and since queens are the only type of bumble bees that can form new colonies, pollen availability directly affects the future bumble bee population size (Burns 2004). Early spring and late fall are often periods with lower floral resources; the presence of flowering plants at these critical times is essential. Laboratory evidence suggests that a diet of more diverse pollen sources early in the season leads to more robust colonies later in the year (Watrous et al. 2019).

Bombus occidentalis is a generalist forager and has been reported to visit a wide variety of flowering plants in Oregon and Washington. The plant genera most commonly associated with B. occidentalis observations or collections from Oregon and Washington include: Cirsium (39 observations), Spiraea (28), Centaurea (21), Solidago (19), Lupinus (18), Chamaenerion (14), Plantago (10), Anaphalis (7), Aquilegia (5), and Erigeron (5) (Williams et al. 2014, Xerces Society et al. 2020). Similarly, in an analysis largely based on records from California, Thorp et al. (1983) report that B. occidentalis records are primarily associated with plants in the Leguminosae (=Fabaceae), Compositae (=Asteraceae), Rhamnaceae, and Rosaceae families. Note that

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these floral associations do not necessarily represent B. occidentalis’ preference for these plants over other flowering plants, but rather may represent the abundance of these flowers in the landscape.

Overwintering Sites: Very little is known about the hibernacula, or overwintering sites, utilized by B. occidentalis, although Hobbs (1968) reported B. occidentalis hibernacula that were two inches deep in a “steep west slope of the mound of earth.” The closely related B. terrestris reportedly hibernates beneath trees (Sladen 1912 in Hobbs 1968).

Threats: The primary threats to B. occidentalis at the sites where it currently exists in Oregon and Washington include: pathogens from commercial bumble bees and other sources, impacts from reduced genetic diversity, and habitat alterations including conifer encroachment (resulting from fire suppression), grazing, and logging. Other threats include pesticide use, competition from managed bees, fire, agricultural intensification, urban development, and climate change. These threats are reviewed below.

In a rangewide study of eight bumble bee species, B. occidentalis and other declining species were associated with increased levels of the fungal pathogen Nosema bombi relative to species that were found to be stable (Cameron et al. 2011a). A recent study investigating the hypothesis, developed by Dr. Robbin Thorp, that an exotic strain of N. bombi was introduced to North American bumble bees via the commercial bumble bee industry found that although the pathogen was likely not a novel or exotic strain, the commercial bumble bees were likely responsible for spreading and amplifying N. bombi throughout North America (Cameron et al. 2016). Pathogens and parasites from other sources, such as RNA viruses from honey bee colonies (Singh et al. 2010), also threaten wild bumble bees (reviewed in Hatfield et al. 2018).

Since B. occidentalis has recently undergone a dramatic decline in range and relative abundance, reduced genetic diversity and other genetic factors reviewed in Zayed (2009) may lead to increased pathogen susceptibility, thus making this species especially vulnerable to extinction (Altizer et al. 2003, Whitehorn et al. 2009). Recent research indicates that populations of B. occidentalis have lower genetic diversity compared to populations of co-occurring stable species (Cameron et al. 2011a, Lozier et al. 2011).

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Modifications to bumble bee habitat from overgrazing by livestock can be particularly harmful to bumble bees (reviewed in Hatfield et al. 2012) by removing floral resources, especially during the mid-summer period when flowers may already be scarce (Hatfield and LeBuhn 2007). In addition, livestock may trample nesting and overwintering sites, or disrupt rodent populations, which can indirectly harm bumble bees. Indirect effects of logging, such as increased siltation in runoff, and recreational activities, such as off-road vehicle use, also have the potential to alter meadow ecosystems and disrupt B. occidentalis habitat.

Additional habitat alterations, such as conifer encroachment resulting from fire suppression (Panzer 2002, Schultz and Crone 1998, Roland and Matter 2007), fire, agricultural intensification (Williams 1986, Carvell et al. 2006, Diekotter et al. 2006, Fitzpatrick et al. 2007, Kosior et al. 2007, and Goulson et al. 2008), urban development (Bhattacharya et al. 2003, Jha and Kremen 2012), and competition from managed bees (including the honey bee, Apis mellifera) (reviewed in Hatfield et al. 2018) may threaten B. occidentalis.

Insecticides, which are designed to kill insects directly, and herbicides, which can remove floral resources, both pose serious threats to bumble bees. Of particular concern are neonicotinoids, a class of systemic insecticides whose toxins are expressed in the nectar and pollen of plants and thus are actively collected by bumble bees. These insecticides are extraordinarily persistent in the environment and exert both lethal and sublethal effects on bumble bees (Whitehorn et al. 2012, reviewed in Hopwood et al. 2012).

Recent evidence suggests that climate change is having landscape scale effects on bumble bee populations (Kerr et al. 2015). A regional analysis suggests that climate change will reduce habitat suitability, particularly at high altitudes, in the Pacific Northwest (Koch et al. 2019). Although B. occidentalis was not identified in this study to be particularly at risk, it was only detected 6 times in the study, likely excluding it from robust analysis (Koch et al. 2019). Since B. occidentalis is currently found primarily in higher elevation sites throughout Oregon and Washington, it may be particularly susceptible to the effects of climate change.

Conservation Considerations: Research: Ongoing efforts are underway at the U.S. Geological Society to assist the U.S. Fish and Wildlife Service in conducting a Species Status

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Assessment for a pending endangered species petition for this species. As part of that effort, Graves et al. (2020) identified several research gaps for this species’ life-history, including: brood initiation, late summer habitat needs, home range size, dispersal needs and patterns, nesting, and overwintering. Some of this research, particularly efforts to better understand nesting and overwintering habitats, are slated to begin in 2021.

Inventory: Once very common in the western United States and western Canada, B. occidentalis has recently undergone a dramatic decline in abundance and distribution and is no longer present across much of the historic range. In order to better understand the causes and extent of this species’ decline, as well as the conservation needs of remaining populations, additional comprehensive surveys of this species at historic and suspected sites are needed throughout Oregon and Washington (see map in Attachment 3). While the PNWBBA has made significant strides in this direction (Xerces Society et al. 2020), Graves et al. (2020) identified priority areas for detection surveys. A map of those high priority sites can be found here.

Management: Protect known and suspected sites from potentially harmful practices, such as intensive livestock grazing, and threats that can interfere with the availability of season-long foraging resources and nesting resources. Limit disease and competition by reducing exposure to honey bee apiaries, and ensuring that placement of apiaries is at least 4 miles from known locations of this species.

Version 2:Prepared by: Katie Lamke and Rich HatfieldXerces Society for Invertebrate Conservation Date: December 2020

Edited by: Candace FallonXerces Society for Invertebrate Conservation Date: December 2020

Version 1:Prepared by: Sarina Jepsen, Xerces Society for Invertebrate Conservation; Map and land ownership analysis by Sarah Foltz JordanXerces Society for Invertebrate ConservationDate: May 2013

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Edited by: Sarah Foltz JordanXerces Society for Invertebrate Conservation Date: May 2013

Final Edits: Rob HuffFS/BLM Conservation Planning CoordinatorDate: February 2014Recommended citation: Lamke, K., R. Hatfield, and S. Jepsen. 2020. Interagency Special Status/Sensitive Species Program (ISSSSP) Species Fact Sheet: Bombus occidentalis. USDA Forest Service Region 6 and USDI Bureau of Land Management Oregon State Office. 26 pp. Available at: https://www.fs.fed.us/r6/sfpnw/issssp/species-index/fauna-invertebrates.shtml       

ATTACHMENTS:(1) References(2) List of pertinent or knowledgeable contacts (3) Map of Oregon/Washington distribution(4) Illustration and photographs of this species(5) Bombus survey protocol, including specifics for this species

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Cameron, Sydney. 2012. Professor, University of Illinois at Champaign-Urbana, IL. Personal communication with Sarina Jepsen, Xerces Society.Cameron S. A., H. M. Hines, and P. H. Williams. 2007. A comprehensive phylogeny of the bumble bees (Bombus). Biological Journal of the Linnean Society 91:161-188.Cameron, S. A., J. D. Lozier, J. P. Strange, J. B. Koch, N. Cordes, L. F. Solter, and T. L. Griswold. 2011a. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Sciences 108:662–667.Cameron, S., S. Jepsen, E. Spevak, J. Strange, M. Vaughan, J. Engler, and O. Byers [Eds.]. 2011b. North American Bumble Bee Species Conservation Planning Workshop Final Report. Available at: http://www.xerces.org/stlouis-iucn-bumblebee-conservation/. Carvell, C., D. B. Roy, S. M. Smart, R. F. Pywell, C. D. Preston, and D. Goulson. 2006. Declines in forage availability for bumblebees at a national scale. Biological Conservation 132:481–489.Diekötter, T., K. Walther-Hellwig, M. Conradi, M. Suter, and R. Frankl. 2006. Effects of landscape elements on the distribution of the rare bumblebee species Bombus muscorum in an agricultural landscape. Arthropod Diversity and Conservation 15: 57-68.Discover Life. 2020. Xylocopa page. Available at: http://www.discoverlife.org/20/q. Accessed 18 Dec 2020.Evans, E., R. W. Thorp, S. Jepsen, and S. H. Black. 2008. Status review of three formerly common species of bumble bee in the Subgenus Bombus. Available at http://www.xerces.org/wp-content/uploads/2009/03/xerces_2008_bombus_status_review.pdf.Fitzpatrick, Ã., T. E. Murray, R. J. Paxton, and M. J. F. Brown. 2007. Building on IUCN Regional Red Lists to Produce Lists of Species of Conservation Priority: a Model with Irish Bees. Conservation Biology 21: 1324–1332.Franklin, H. J. 1913. The Bombidae of the New World. Transactions of the American Entomological Society 38: 177-486.Goulson, D. 2010. Bumblebees: Behavior, Ecology, and Conservation. Oxford University Press. 317 pages.Goulson, D., G. C. Lye, and B. Darvill. 2008. Decline and conservation of bumble bees. Annual Review of Entomology 53:191–208.Graves, T. A., W.M. Janousek, S.M. Gaulke, A.C. Nicholas, D.A. Keinath, C.M. Bell, S. Cannings, R.G. Hatfield, J.M. Heron, J.B. Koch, H.L. Loffland, L.L. Richardson, A.T. Rohde, J. Rykken, J.P. Strange, L.M. Tronstad, and C.S. Sheffield. 2020. Western bumble bee: declines in the continental United States and range‐wide information gaps. Ecosphere 11(6): 99.

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http://www.fs.fed.us/wildflowers/pollinators/documents/BumbleBeeGuide2012.pdf. Kosior, A., W. Celary, P. Olejniczak, J. Fijal, W. Krol, W. Solarz, and P. Plonka. 2007. The decline of the bumble bees and cuckoo bees (Hymenoptera: Apidae: Bombini) of Western and Central Europe. Oryx 41:79.Lozier, J. D., J. P. Strange, I. J. Stewart, and S. A. Cameron. 2011. Patterns of range-wide genetic variation in six North American bumble bee (Apidae: Bombus) species. Molecular Ecology. Retrieved February 1, 2013, from http://onlinelibrary.wiley.com/doi/10.1111/j.1365-294X.2011.05314.x/full.Macfarlane R. P., K. D. Patten, L. A. Royce, B. K. W. Wyatt, and D. F. Mayer. 1994. Management potential of sixteen North American bumble bee species. Melanderia 50:1-12.Memmott J., P. G. Craze, N. M. Waser, and M. V. Price. 2007. Global warming and the disruption of plant-pollinator interactions. Ecology Letters 10:710-717.Michener, C. D. 2000. The Bees of the World. John Hopkins University Press. 913 pages.NatureServe. 2020. Bombus occidentalis Greene, 1858. NatureServe Explorer [web application]. NatureServe, Arlington, Virginia. Available at: https://explorer.natureserve.org/ [Accessed November 2020].Plath O. E. 1922. Notes on the nesting habits of several North American bumblebees. Psyche 29(5-6):189-202.ORBIC (Oregon Biodiversity Center). 2013 Rare, Threatened, and Endangered Species of Oregon. July 2013. Available at http://orbic.pdx.edu/rte-species.html (Accessed 6 February 2014). Owen, R. E., T.L. Whidden, and R.C. Plowright. 2010. Genetic and morphometric evidence for the conspecific status of the bumble bees, Bombus melanopygus and Bombus edwardsii. Journal of Insect Science 10: 109.Panzer, R. 2002. Compatibility of prescribed burning with the conservation of insects in small, isolated prairie reserves. Conservation Biology 16:1296–1307.Roland, J., and S. F. Matter. 2007. Encroaching forests decouple alpine butterfly population dynamics. Proceedings of the National Academy of Sciences 104:13702–13704.Schultz, C. B., and E. E. Crone. 2008. Note: using ecological theory to advance butterfly conservation. Israel Journal of Ecology and Evolution 54:63–68.Sheffield, C. S., L. Richardson, S. Cannings, H. Ngo, J. Heron, and P.H. Williams. 2016. Biogeography and designatable units of Bombus occidentalis Greene and B. terricola Kirby (Hymenoptera: Apidae) with implications for

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conservation status assessments. Journal of Insect Conservation 20(2): 189–199.Singh R., A. L. Levitt, E. G. Rajotte, E. C. Holmes, N. Ostiguy, D. vanEngelsdorp, W. I. Lipkin, C. W. dePamphilis, A. L. Toth, and D. L. Cox-Foster. 2010. RNA viruses in hymenopteran pollinators: Evidence of inter-taxa virus transmission via pollen and potential impact on non-Apis hymenopteran species. PLoS ONE 5(12): e14357. doi:10.1371/journal.pone.0014357. Richardson, L.L. 2019. Bumble Bees of North America: Data Contributors [Data set]. http://www.leifrichardson.org/bbna.htmlThomson, J. D. 2010. Flowering phenology, fruiting success and progressive deterioration of pollination in an early-flowering geophyte. Philosophical Transactions of the Royal Society B: Biological Sciences 365:3187–3199.Thorp, Robbin. 2013. Professor emeritus, University of California, Davis. Personal communication with Sarina Jepsen, Xerces Society.Thorp, R. W., D. S. Horning, and L. L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23: viii. Thorp, R. W., and M. D. Shepherd. 2005. Profile: Subgenus Bombus. Red list of pollinator insects of North America. Available online: [USFWS] 2020. United States Fish and Wildlife Service. Environmental Conservation Online System (ECOS). Online database. Available at: https://ecos.fws.gov/ecp0/reports/ad-hoc-species-report-input [Accessed November 2020].Watrous, K. M., M.A. Duennes, and S.H. Woodard. 2019. Pollen diet composition impacts early nesting success in queen bumble bees Bombus impatiens Cresson (Hymenoptera: Apidae). Environmental Entomology. https://doi.org/10.1093/ee/nvz043Whitehorn, P. R., M. C. Tinsley, M. J. F. Brown, B. Darvill, and D. Goulson. 2009. Impacts of inbreeding on bumblebee colony fitness under field conditions. BMC Evolutionary Biology 9:152.Whitehorn P., S. O'Connor, F. Wackers, and D. Goulson. 2012. Neonicotinoid pesticide reduces bumble bee colony growth and queen production. Science, 336(6079):351-2. doi: 10.1126/science.1215025. Williams, P. H. 1986. Environmental change and the distributions of British bumble bees (Bombus Latr.). Bee world 67:50–61.Williams P. H., M. J. F. Brown, J. C. Carolan, J. An, D. Goulson, A. Murat Ayetkin, L. R. Best, A. M. Byvaltsev, B. Cederberg, R. Dawson, J. Huang, M. Ito, A. Monfared, R. H. Raina, P. Schmid-Hempel, C. S. Sheffield, P. Sima, and Z. Xie. 2012. Unveiling cryptic species of the bumblebee subgenus Bombus

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s. str. Worldwide with COI barcodes (Hymenoptera: Apidae). Systematics and Biodiversity, http://dx.doi.org/10.1080/14772000.2012.664574Williams, P. H., R. W. Thorp, L. L. Richardson, and S. Colla. 2014. Guide to the Bumble Bees of North America. Princeton University Press.Xerces Society, Idaho Fish and Game, Washington Fish and Wildlife, 2020. PNWBumblebeeatlas.org, Data accessed from Bumble Bee Watch. Available from http://www.bumblebeewatch.org/app/#/bees/lists. Accessed: 10/23/2020.Xerces Society, Idaho Fish and Game, Washington Fish and Wildlife. 2018. Point Surveys. The Pacific Northwest Bumble Bee Atlas. https://www.pnwbumblebeeatlas.org/point-surveys.htmlXerces Society. 2012. Database of records from Bumble Bee Citizen Monitoring Project (2008-2012). Maintained by Rich Hatfield, Xerces Society.Zayed, A. 2009. Bee genetics and conservation. Apidologie 40:237–262.Zayed, A., and L. Packer. 2005. Complementary sex determination substantially increases extinction proneness of haplodiploid populations. Proceedings of the National Academy of Sciences of the United States of America 102:10742–10746.

Map references:[BLM] Bureau of Land Management. 2020. GeoBOB GIS export provided to Candace Fallon, the Xerces Society, by Darci Rivers-Pankratz, Interagency Special Status/Sensitive Species Program, 23 November 2020.

[USFS] US Forest Service. 2020. List of observations collected by Sandra DeBano, Oregon State University, at Meadow Creek in the USFS Starkey Experimental Forest and Range provided to Rich Hatfield, the Xerces Society, by Andy Broadhead, USFS, 3 November 2020. [USFS] US Forest Service. 2020. NRM GIS export provided to Candace Fallon, the Xerces Society, by Carol Hughes, Interagency Special Status/Sensitive Species Program, 29 October 2020.

Williams, P. H., R. W. Thorp, L. L. Richardson, and S. Colla. 2014. Guide to the Bumble Bees of North America. Princeton University Press.

Xerces Society. 2020. ISSSSP Curation Database. Database queried, November 2020. Unpublished.

Xerces Society, Idaho Fish and Game, Washington Fish and Wildlife, 2020. PNWBumblebeeatlas.org, Data accessed from Bumble Bee Watch. Available

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from http://www.bumblebeewatch.org/app/#/bees/lists. Accessed: 10/23/2020

ATTACHMENT 2: List of pertinent or knowledgeable contacts James Strange, USDA ARS Logan Bee LabPaul Williams, Natural History Museum, LondonMichael Otterstatter, Health CanadaCory Sheffield, Royal Saskatchewan MuseumJames Thomson, University of TorontoSarina Jepsen, Xerces SocietyRich Hatfield, Xerces Society Jeff Lozier, University of Alabama

ATTACHMENT 3: Map of species distribution

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Records of Bombus occidentalis in Oregon and Washington, relative to Forest Service and BLM lands.

ATTACHMENT 4: Illustration and photographs of species18

B. occidentalis (female) worker, nominate color form. Although twelve color forms for females of this species have been described (Franklin 1913), the color form illustrated above is representative of B. occidentalis that occur in Oregon and Washington. Both the nominate form and another color form that occurs in Oregon, Washington, and nearby areas are represented in the photographs, below. Illustration by Elaine Evans, The Xerces Society. Used with permission.

Bombus occidentalis, nominate color form, adult female, dorsal view, from Mt. Hood National Forest, Oregon, September 2015. Photograph by Rich Hatfield, The Xerces Society. Used with Permission.

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Bombus occidentalis, adult female, side view. Photograph taken in Johnson’s Landing, British Columbia by Gail Spitler, May 2010.

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Bombus occidentalis, adult male, side view. Photograph taken on the Wallowa-Whitman National Forest, 2018. Photo by the Xerces Society/Rich Hatfield.

ATTACHMENT 5: Hymenoptera: Apoidea Survey Protocol, including specifics for this species

By Katie Hietala-Henschell and Rich Hatfield

Taxonomic group: Apoidea

Note: Single-species targeted surveys for native bees, with the exception of Bombus sp., are likely to be logistically challenging. Many native bees have features that require specialized equipment (stereoscope) and an expert to be properly identified to species. There is a scarcity of bee taxonomists in the country, and identifications can take significant time and, depending on the number of specimens, require significant expense. Also, implementing

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standardized survey protocols for one species (depending on the method and the expertise of the surveyor) can result in a large bycatch of other native bees, as well as other flower visiting insects like flies and wasps. While this is unlikely to harm insect populations, if there is not a plan for the identification, storage and curation of these specimens, such bycatch would be ill-advised. However, since little is known about many native bee species, surveying for this species and others could be done as part of a larger effort to assess the native bee community of an area.

Where: Native bees utilize a diversity of terrestrial habitats. Many species have highly specific feeding preferences while other species exhibit more general feeding patterns. When surveying new areas, seek out places with adequate food (e.g. diverse wildflowers and flowering trees) and habitat (e.g. native plants, undisturbed ground, dead wood) to sustain a population.

When: Survey timing will be species-specific occurring within the window of the target species’ documented activity but can occur in the spring, summer, and/or fall. Adult life spans can be relatively short, limiting trapping to a brief period; however, some bee species can live in the adult stage for several months to a year.

How to Survey: If possible, all sites should be surveyed during the following environmental conditions:

Minimum temperature: Above 60°F (~15°C)Cloud cover: Partly sunny or better. On cooler days the sun can play a very important role in bee activity. Wind: Low wind, less than 8 MPH. Precipitation: No rain and dry vegetation.Time of day: Between 10AM and 4PM. Success is most likely during the warmest parts of the day. However, especially in more arid conditions, some species are known to be active at very early times of day. The surveyor needs to ensure that the timing and survey methodology overlap with the life histories of the species of interest. Time of year: Varies by region. If known, historical and/or current sites could be checked before the start of the planned survey period, as flight times may vary due to weather conditions in the spring and early summer.

Native bees have a varied natural history and abundance can be site-specific. No single method of monitoring is suitable to sample all species. In

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order to compare bee communities over time, sampling efforts should be standardized, replicated, and repeated (Westphal et al. 2008). There are multiple sampling techniques that can be used independently or in combination, including: sweep netting (Droege et al. 2015), pan traps (Droege et al. 2010), trap nesting (Guisse and Miller 2011), and Malaise or vane traps (Geroff et al. 2014). Research indicates that a combination of methods is likely to provide the most thorough sample of the bee population. Geroff et al. (2014) provide a thorough quantitative analysis of many of the passive trapping systems mentioned above. More recent research suggests that passive sampling methods, like pan trapping, have taxonomic biases, fail to adequately measure bee abundances, and also prevent gathering important floral host plant information (Portman et al. 2020). As such, researchers need to be careful to choose the monitoring method that will most closely match the needs of the desired outcome of the monitoring program.

There are pros and cons to each sampling method, therefore utilizing multiple sampling techniques will likely enhance sampling efforts resulting in a more complete inventory (Westphal et al. 2008, Popic et al. 2013, McCravy et al. 2016). However, the methods need to be complementary, and not duplicative (Portman et al. 2020) to avoid unnecessary bycatch, and a complete survey of the fauna – or at least the fauna of interest. The Very Handy Bee Manual (Droege et al. 2015) provides detailed instructions on collecting, preparing, and pinning bees for long term preservation and/or deposition in formal collections. Simplified monitoring protocols, focused on observational data, and data sheets are available to assess bee diversity and abundance by counting the total number of native bees (Ward et al. 2014).

After choosing the appropriate sampling technique(s) at a potential site record the site name, survey date and time, elevation, aspect, legal location, latitude and longitude coordinates of site, weather conditions, and a thorough description of habitat, including vegetation types, vegetation canopy cover, suspected or documented host plant species, and/or landscape contours (including direction and angle of slopes). Photographs of habitat are also a good supplement for collected specimens and, if taken, should be cataloged and referred to on the insect labels. Collection labels should include the following information: date, time of day, collector, and detailed locality (including geographical coordinates, mileage from named location, elevation). Complete determination labels include the species name, sex (if known), determiner name, and date determined. Mating pairs

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should be indicated as such and stored together, if possible. Record data for sites whether bees are seen or not. In this way, overall search effort is documented, in addition to new sites.

Species-specific Survey Details: Bombus occidentalis

Where: Although this species historically occurred throughout western North America, its range has dramatically declined in recent years. In Oregon and Washington, B. occidentalis was once widely distributed, but now appears to be primarily restricted to higher elevation sites east of the Cascade Crest (Xerces Society et al. 2020, Cameron et al. 2011). Additional surveys at historic and potential sites on National Forests and BLM districts where B. occidentalis is suspected or documented are needed to identify this bee’s current distribution in Oregon and Washington.

Meadows and grasslands with abundant floral resources are the appropriate habitat for this species. Bombus occidentalis is a generalist forager and has been reported to visit a wide variety of flowering plants in Oregon and Washington. The plant genera most commonly associated with B. occidentalis observations or collections from Oregon and Washington include: Cirsium (39 observations), Spiraea (28), Centaurea (21), Trifolium (20), Solidago (19), Lupinus (18), Chamaenerion (14), Plantago (10), Anaphalis (7), Aquilegia (5), and Erigeron (5) (Williams et al. 2014, Xerces Society et al. 2020). Similarly, in an analysis largely based on records from California, Thorp et al. (1983) reports that B. occidentalis is primarily associated with plants in the Leguminosae (=Fabaceae), Compositae (=Asteraceae), Rhamnaceae, and Rosaceae families. Although B. occidentalis has a short tongue, and can therefore most easily access open flowers with short corollas, it does visit flowers with longer corollas to rob nectar (a behavior in which the bee chews a hole in the base of the corolla to obtain nectar without actually achieving pollination).

Although meadows with flowers in the genera and families noted above may be targeted for surveys, it is important to note that these floral associations do not necessarily represent B. occidentalis’ preference for these plants over other flowering plants, but rather may represent the abundance of these flowers in the landscape.

When: Surveys should target the peak flight period for female workers, which is in early August for B. occidentalis in California (Thorp et al. 1983)

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and mid-August for B. occidentalis in Utah (Koch et al. 2012). However, the peak flight period at a specific site will vary by elevation. Graves et al. (2020) determined that peak detection for B. occidentalis throughout its range was mid-July. The colony life cycle for B. occidentalis can begin as early as February and, in some cases, can last until late November. According to Thorp et al. (1983), the flight period for B. occidentalis queens in California ranges from early February to late November, peaking in late June and late September. The flight period for workers and males in California is from early April to early November; worker abundance peaks in early August, and male abundance peaks in early September (Thorp et al. 1983).

How to survey:Identification: In Oregon and Washington, this species is readily identified by the white hairs on the apex of the fourth abdominal segment, as well as on the fifth and sixth segments. Additional distinguishing features are available in Koch et al. (2012) and are provided in this ISSSSP Species Fact Sheet. The Pacific Northwest Bumble Bee Atlas bumble bee survey protocol is available online (Xerces Society et al. 2018).

References (Survey Protocol only):Cameron, S. A., J. D. Lozier, J. P. Strange, J. B. Koch, N. Cordes, L. F. Solter, and T. L. Griswold. 2011. Patterns of widespread decline in North American bumble bees. Proceedings of the National Academy of Sciences 108:662–667.Cane, J. H., R. L. Minckley, and L. J. Kervin. 2000. Sampling bees (Hymenoptera: Apiformes) for pollinator community studies: pitfalls of pan-trapping. Journal of the Kansas Entomological Society 73:225–231. Droege, S., V.J. Tepedino, G. Lebuhn, W. Link, R.L. Minckley, Q. Chen, and C. Conrad. 2010. Spatial patterns of bee captures in North American bowl trapping surveys. Insect Conservation and Diversity 3: 15-23.Droege, S., J. Green, D. Green, G. Scarpulla, L. Sellers, and T. Zarrillo. 2015. The very handy manual: how to catch and identify bees and manage a collection. Available at: http://bio2.elmira.edu/fieldbio/beemanual.pdf [Accessed November 2020). Gardner, J.D. and M. Spivak. 2014. A survey and historical comparison of the Megachilidae (Hymenoptera: Apoidea) of Itasca State Park, Minnesota. Annals of the Entomological Society of America 107(5): 983-993.Geroff, R.K., J. Gibbs, and K.W. McCravy. 2014. Assessing bee (Hymenoptera: Apoidea) diversity of an Illinois restored tallgrass prairie: methodology and conservation considerations. Journal of Insect Conservation 18: 951-564.

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Graves, T. A., W.M. Janousek, S.M. Gaulke, A.C. Nicholas, D.A. Keinath, C.M. Bell, S. Cannings, R.G. Hatfield, J.M. Heron, J.B. Koch, H.L. Loffland, L.L. Richardson, A.T. Rohde, J. Rykken, J.P. Strange, L.M. Tronstad, and C.S. Sheffield. 2020. Western bumble bee: declines in the continental United States and range‐wide information gaps. Ecosphere 11(6):99.Goulson, D. 2010. Bumblebees: Behavior, Ecology, and Conservation. Oxford University Press. 317 pages.Guisse, J.K. and D.G. Miller III. 2011. Distribution and habitat preferences of Osmia lignaria (Hymenoptera: Megachilidae) and associated cavity-nesting insects in California’s Sierra Nevada foothills adjacent to the Sacramento Valley. The Pan-Pacific Entomologist 87(3): 188-195. Koch, J. B., J. P. Strange, and P. H. Williams. 2012. Bumble Bees of the Western United States. USDA Forest Service and the Pollinator Partnership. Available at: http://www.fs.fed.us/wildflowers/pollinators/documents/BumbleBeeGuide2012.pdfLeBuhn, G., T. Griswold, R. Minckley, S. Droege, T. Roulston, J. Cane, F. Parker, S. Buchmann, V. Tepedino, N. Williams, C. Kremen, and O. J. Messinger. 2003. A standardized method of monitoring bee populations—the Bee Inventory (BI) plot. Available at: http://online.sfsu.edu/~beeplot/pdfs/Bee%20Plot%202003.pdf McCravy, K.W., R.K. Geroff, and J. Gibbs. 2016. Malaise trap sampling efficiency for bees (Hymenoptera: Apoidea) in a restored tallgrass prairie. Florida Entomologist 99(2): 321-323. Popic, T.J., Y.C. Davila, G.M. Wardle. 2013. Evaluation of common methods for sampling invertebrate pollinator assemblages: net sampling out-perform pan traps. PLoS ONE 8(6): e66665.Portman, Z. M., B. Bruninga-Socolar, and D.P. Cariveau. 2020. The state of bee monitoring in the United States: A call to refocus away from bowl traps and towards more effective methods. Annals of the Entomological Society of America 113(5):337–342.Roulston, T. H., S. A. Smith, and A. L. Brewster. 2007. Short communication: a comparison of pan trap and intensive net sampling techniques for documenting a bee (Hymenoptera: Apiformes) fauna. Journal of the Kansas Entomological Society 80:179–181.Stephen, W. P. 1957. Bumble bees of western America. Oregon State University. 161 pages. Thorp, R. W., D. S. Horning and L. L. Dunning. 1983. Bumble bees and cuckoo bumble bees of California (Hymenoptera: Apidae). Bulletin of the California Insect Survey 23: viii. Ward, K., D. Cariveau, E. May, M. Roswell, M. Vaughan, N. Williams, R. Winfree, R. Isaacs, and K. Gill. 2014. Streamlined bee monitoring protocol for

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assessing pollinator habitat. 16 pp. Portland, OR: The Xerces Society for Invertebrate Conservation. Westphal, C., R. Bommarco, G. Carre, E. Lamborn, N. Morison, T. Petanidou, S.G. Potts, S.P.M. Roberts, H. Szentgyorgyi, T. Tscheulin, B.E. Vaissiere, M. Woyciechowski, J.C. Biesmeijer, W.E. Kunin, J. Settele, and I. Steffan-Dewenter. 2008. Measuring bee diversity in different European habitats and biogeographical regions. Ecological Monographs 78(4): 653-671.Williams, P. H., R. W. Thorp, L. L. Richardson, and S. Colla. 2014. Guide to the Bumble Bees of North America. Princeton University Press.Xerces Society, Idaho Fish and Game, Washington Fish and Wildlife. 2020. PNWBumblebeeatlas.org, Data accessed from Bumble Bee Watch. Available from http://www.bumblebeewatch.org/app/#/bees/lists. Accessed: 10/23/2020.Xerces Society, Idaho Fish and Game, Washington Fish and Wildlife. 2018. Point Surveys. The Pacific Northwest Bumble Bee Atlas. https://www.pnwbumblebeeatlas.org/point-surveys.htmlXerces Society. 2012. Database of records from Bumble Bee Citizen Monitoring Project (2008-2012). Maintained by Rich Hatfield, Xerces Society.

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