Many pest ant species are known to tend honeydew producing homoptera. It is thought that utilization of this carbohydrate resource allows pest ant species, such as the Argentine ant Linepithema humile, to maintain their characteristically high worker densities in their introduced range. Argentine ants were observed tending the native honeydew producing Terrapin scale, Mesolecanium nigrofasciatum, on red maple trees, in a North Carolina industrial park. Red maple trees outside of the Argentine ant infestation showed no sign of Terrapin scale infestation. We investigated the nature of the mutualism between these two organisms. When the Argentine ants were excluded, the Terrapin scale populations decreased significantly. When access to the Terrapin scale was denied, Argentine ant densities around the infested red maples declined. These results suggest that effective control of honeydew producing homoptera may aid in the prevention or reduction the incidence of pest ant infestations, especially around structures.