The habits of our native North American ptinids are practically unknown. A few species are thought to breed in bark or dead twigs, others in the roots of dry grass. As far as is known to the writers, there is no published life history of any native species and what is known of ptinid biology has generally been derived from a study of the species injurious to stored food and plant products. For this reason it has seemed worthwhile to make known the habits of Ptinus californicus Pic, a species which lives as a depredator in the nests of wild bees. Although the association of ptinids with bees has been previously recorded for a few European species, this appears to be the first time it has been observed for any American form.