A population ofOsmia cornutaLatr. was trapped in northern Spain during 1984, transported to the United States, quarantined, exposed to various temperature regimes through summer months, and placed in California almond orchards through winter months. Results of this study demonstrated that bees overwintered in commercial almond orchards emerged in synchrony with almond bloom; gregarious nesting was expressed; immatures developed normally on provisions composed mostly of almond pollen and nectar resources; prewintering temperatures affected winter survival of parent bees; and populations that had the highest rates of winter mortality produced the fewest number of cells per emerged female.