Delphia, Caey M.2023-09-212023-09-212023-05Casey M. Delphia "Chelostoma Latreille, 1809 (Hymenoptera: Megachilidae) of Montana, including first records of the introduced bees Chelostoma campanularum (Kirby, 1802) and Chelostoma rapunculi (Lepeletier, 1841)," The Pan-Pacific Entomologist, 99(2), 153-168, (30 June 2023)0031-0603https://scholarworks.montana.edu/handle/1/18110The megachilid bees of the genus Chelostoma Latreille, 1809 in Montana, U.S.A., are reviewed. Two Palearctic species, Chelostoma (Foveosmia) campanularum (Kirby, 1802) and Chelostoma (Gyrodromella) rapunculi (Lepeletier, 1841), are reported for the first time from Montana. The Montana specimens represent a range expansion from southeastern Michigan for C. campanularum and from northeastern Illinois for C. rapunculi. These collections appear to represent an established local population for C. campanularum with specimens from multiple dates, years, and locations in Bozeman, Montana; specimens of C. rapunculi have only been found in one location and year. The habitat, distribution, and potential ecological impacts of establishment of these two non-native species in Montana are discussed. An identification key to the Chelostoma of Montana is provided.en-UScopyright Pacific Coast Entomological Society 2023http://pcentsoc.org/Apoideacavity-nestingnon-native speciesPalearcticpollinatorsrange expansionsolitary beesArticle