Coptotermes formosanus Shiraki are economically important subterranean termites, particularly in the Southeastern United States where they are considered invasive. Where two C. formosanus populations met, aggressive encounters resulted in blockages in tunnels, but reinvading termites unblocked obstructions or constructed new tunnels. Experiments in planar arenas in which one population of C. formosanus was baited resulted in elimination of baited termites and subsequent reinvasion of territory by neighboring termites. Territories held by unbaited neighboring termites increased significantly, nearly doubling after reinvasion. Reinvading termites consumed baits left by baited colonies and were eliminated.