Recently, epidermal cells of flowers have gotten a lot of attention due to their diverse and unique roles in plant-pollinator interactions. In this study, we investigated the role of the epidermal cells in the pollination of the protogynous trap flowers of Aristolochia liukiuensis and A. shimadae (Aristolochiaceae). The flowers attract and capture dipteran pollinators during the initial female stage and release them after changing their sexual stage to male. We found that the flower surface microstructure composed of conical epidermal cells that present during the female stage disappear during the male stage. Our experiment using pollinator flies revealed a significant difference in slipperiness between the female and male stages, which correlates with the changes in the epidermal cells, potentially controlling the trap and release of the pollinators. These cells also secreted a liquid containing volatile organic compounds (VOCs) from their tops during flowering, composed of various terpenes and aldehydes that could potentially attract flower-visiting flies. Overall, our results suggest that epidermal cells play a central role in pollination of Aristrochia spp. by attracting pollinators, trapping and releasing pollinators.