Bombus (Psithyrus) ashtoni ( Cresson 1864 )

Gibbs, Jason, Ascher, John S., Rightmyer, Molly G. & Isaacs, Rufus, 2017, The bees of Michigan (Hymenoptera: Apoidea: Anthophila), with notes on distribution, taxonomy, pollination, and natural history, Zootaxa 4352 (1), pp. 1-160 : 41-42

Bombus (Psithyrus) ashtoni ( Cresson 1864) ( bohemicus group)

County records: Alcona, Alger, Allegan, Alpena, Arenac, Baraga, Barry, Bay, Benzie, Charlevoix, Cheboygan, Chippewa, Clare, Clinton, Crawford, Delta, Dickinson, Emmet, Gladwin, Gogebic, Grand Traverse, Gratiot, Houghton, Huron, Ingham, Iosco, Iron, Isabella, Kalamazoo, Kalkaska, Keweenaw, Lake, Leelanau, Lenawee, Livingston, Luce, Mackinac, Manistee, Marquette, Mason, Mecosta, Menominee, Midland, Missaukee, Montmorency, Oakland, Ogemaw, Ontonagon, Osceola, Oscoda, Otsego, Presque Isle, Roscommon, Schoolcraft, Shiawassee, Washtenaw, Wexford.

Notes. Bombus ashtoni is a social parasite of B. affinis and B. terricola ( Plath 1922, 1927). The severe declines in B. affinis and range contractions to the north of B. terricola ( Cameron et al. 2011) imply even greater declines in B. ashtoni , decline of which was first noted in the late 1990s at Ithaca, Tompkins Co., New York by JSA (pers. obs.). To our knowledge, no specimen has been collected in Michigan since at least 1993 (OSUC record), but there has been a lack of recent collections in the UP and NLP where B. terricola is still present. Williams et al. (2014) treat B. ashtoni as a junior synonym of B. bohemicus Seidl, 1838 , a relatively common species in the Palaearctic region. There are subtle differences between the two in male genitalia ( Williams 1991), but DNA sequence data show few differences ( Cameron et al. 2007; Williams et al. 2014). Because of this synonymy, Hatfield et al. (2016) list this species as data deficient due to the need for a global analysis, although the North American populations are recognized as critically endangered. Lack of recent records in both specimen and image databases (e.g., http:// bugguide.net) validates concern about the status of North American populations of this bee.