Abstract For solitary bees, nesting substrate availability may limit population growth. Here, we investigate the of a locally abundant bee Osmia conjuncta Cresson (Hymenoptera: Megachilidae) in empty shells exotic snails, Cepaea spp. Held (Stylommatophora: Helicidae), Hamilton, Ontario, Canada. A literature review determined that O. was sparsely distributed throughout its range, with low relati...