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.