Ant fauna on Mallotus japonicus, a shrub with extrafloral nectaries, was investigated in two types of habitat (the villages and the forest-edges) on subtropical Okinawa Island, Japan. Twenty and 16 ant species were found, including 11 and 6 tramp species in the villages and in the forest-edges, respectively. Occurrence of tramp species was higher in the villages than in the forest edges, supporting the idea that tramp species tend to dominate in disturbed habitats. Nevertheless, the richness of native ants was almost the same across the two habitat types. Consequently, the ant species diversity on M. japonicus appeared higher in the villages. However, monitoring has to be continued to determine whether the above findings represent a stable phenomenon of the community or just a temporary state.