The Ceylon birdwing is most active during the morning and early afternoon (3) (5). The butterfly feeds on the nectar of flowers such as Hibiscus, Poinciana (Caesalpinia pulcherrima) and Bougainvillea (3), and the larvae found on the leaves of Aristolochia plants (3) (6).
Orange-yellow eggs are laid singly on the young leaves and shoots of the Aristolochia food plants, which are then voraciously devoured by the young caterpillars after hatching (3) (6). Feeding upon these plants also serves as a defensive mechanism as they contain certain chemicals that make the caterpillars toxic and therefore unpalatable to most predators (7). The caterpillars eventually pupate and undergo metamorphosis into adult butterflies, and maintain these toxic chemicals in their tissues into adulthood (7). The chrysalis of this species is dark brownish-yellow, or greenish-yellow in some individuals, and its leaf-like appearance helps camouflage it amongst the vegetation from potential predators (3). Troides birdwings typically pupate on the twigs or stems of plants close to the larval food plant or on the food plant itself (3).