Specialist pollinators are commonly assumed to make important contributions to the reproduction and evolution of their floral host, but most specialists share their host with several to many generalist pollinators as well. In such cases, the effect of specialists may be swamped out by generalists, regardless of the effectiveness of specialists as pollinators. We studied the pollination dynamics of specialist and generalist pollinators on a shared host, Physalis longifolia ssp. subglabrata, at a field site in northern Virginia during the summer of 2004. Floral visitors included 11 generalist bee species (Bombus spp., 7 halictid species, and the cleptoparasite Epeolus bifasciatus) and one specialist bee species, Colletes latitarsis. The specialist was the only species to be found primarily on Physalis within the plant community and accounted for over 50% of the individuals captured on Physalis during a community-wide pollinator survey. During Physalis plot observations, the specialist accounted for the most plot visits, the most floral visits per plot visit and the greatest success at initiating fruit production from single visits to virgin flowers. During a mark-recapture study, the specialist was the only species recaught (27 of 82 marked individuals), but it seldom moved between plots, even though the nearest plot pair was separated by only 30 meters. These data reveal that the specialist predominated as a pollinator at this site, despite the presence of numerous generalists. The role of generalists, however, still cannot be completely discounted: generalist visits were constant, though infrequent, and the flowering season of Physalis extends beyond that of its specialist pollinator.