Papilio demodocus

Courtship is more or less the same in all Papilionidae. Once a female enters the visual field of a male, the male moves quickly to hover over her so that his wings beat rapidly. The female is then induced to land so that the male can attempt to mate with her. There are various ways in which the male entices the female, including visual, olfactory, tactile, and auditory cues. Of particular interest is the use of olfactory cues. Male butterflies produce pheromones from different structures, such as that of the anal fold of the hindwing, that cause the females to perform the appropriate response. Sometimes, however, females choose to reject a male's attempt at mating, often because she has already mated. She can do so by either avoiding his approach or, if she lands, she will flap her wings quickly and deliberately all while raising her abdomen until the male flies away. In this way, courtship is primarily a female's choice. Furthermore, it has been observed that females also produce a pheromone that aids males in determining whether a female has already mated or not.

This species primarily mates via the lek system, in which there are aggregations of males on small mating territories. When the female reaches the lek, she changes her behavior so that she helps the males to detect her by performing a long and obvious circular flight. The species operates on a polygynous system in which one male has the ability to mate with several females in one breeding season. In Papilio glaucus, that which is of the same genus of this species, the lack of male-male competition, strong rapid flight, dispersed abundant food, and oviposition sights helped to support the idea of mating system based on polygyny. The females are prevented from mating with other males when the male emits a sphragis, which prevents other males from mating with the female, ensuring that only the sperm from this male fertilizes the eggs. The physical act of copulation takes between one half hour to two hours. During this time, the male spermatophore is transferred to the female's bursa. The spermatophore is then absorbed and its nutrient (protein) contents are given to the female's eggs as a food source. For this reason, the male makes an indirect investment to his offspring, given that he offers them a food source, being beneficial to the female given that she risks less of her own well-being to bear her offspring. Therefore, a male is considered more fit with a larger ejaculation, given that he allows his offspring to feed so that his own genes may be passed on efficiently.