Pheromonal advertisement of a nuptial gift by a male moth (Utetheisa ornatrix).

Male Utetheisa ornatrix produce a courtship pheromone (hydroxydanaidal) that they derive from systemic pyrrolizidine alkaloid of plant origin. Pheromone titers in males correlate with systemic levels of alkaloid and with the quantity of alkaloid transmitted to the female at mating. The male's emission of pheromone during courtship may therefore communicate his possession of protective alkaloids and his capacity to provision the female. By mating preferentially with males endowed with hydroxydanaidal, females may ensure their acquisition of an alkaloidal gift for use in egg defense.

Biparental defensive endowment of eggs with acquired plant alkaloid in the moth Utetheisa ornatrix.

The eggs of Utetheisa ornatrix contain pyrrolizidine alkaloids. These compounds are contributed by both parents, who sequester them as larvae from their food plants. Females receive alkaloid from the males at mating, apparently by seminal infusion, and transmit this alkaloid together with alkaloid of their own to the eggs. Field and laboratory tests showed that the alkaloids protect eggs from predators. The alkaloidal contribution of the male, although smaller than that of the female, itself provides significant egg protection. A previously identified pheromone, derived by the male from the alkaloid and emitted during precopulatory behavior, may announce the male alkaloidal worth to the female.

Paternal allocation of sequestered plant pyrrolizidine alkaloid to eggs in the danaine butterfly, Danaus gilippus.

Pyrrolizidine alkaloid sequestered by adult male Danaus gilippus from plants is transferred in large measure to the female at mating, and by the female to the eggs. The eggs, presumably, are protected as a result. The male's courtship pheromone, danaidone, derived from the sequestered alkaloid, may function to advertise the male's alkaloid-donating capacity.