Papilio polytes shows female-limited Batesian mimicry. On Okinawa, one mimicry model is an unpalatable Pachliopta aristolochiae, which wasn’t distributed on the island until 1993. The average white spot size among specimens collected during 1961 to 2016　was unchanged before the model’s establishment but has rapidly increased since then. However, white spot size, suggested as a maternally heritable trait, showed greater variance after the model’s establishment than before. This suggests that before 1993, white spot size in this population wasn’t selectively neutral but an adaptive trait for mimicking an unpalatable native Byasa alcinous, which looks like P. aristolochiae if the hind-wing white spot is added. Thus, some females have switched their model to the new one after 1993.