The rapid release of sex pheromone reflects increasing willingness of female moths to mate

Abstract

It is generally believed that female adults release sex pheromone to attract males in its calling behavior for mating. The female Helicoverpa armigera moth has a grade 1 ovary the day after emergence and develops into matured grade 3 on day 1. Mating peak is at Day 1 and 2, 1:00 of the circadian rhythm. The extrusion percentage and time of the ovipositor, typical calling signal, are lengthened as age increases, with the highest after Day 3 of age. The ovipositor extrusion elevates the release rate of sex pheromone by enlarging the releasing area, and after extrusion, the release rate increases with increasing ambient temperature. The peak of pheromone emission is on Day 3, 3:00 of the circadian rhythm. Mating time is earlier than pheromone biosynthesis, emission and release in female moths. After mating, the pheromone titer drops to a trace level before returning to its original level after 3 days. The activity time of male moths to sex pheromone is longer than that of females. We conclude that the accelerated release of sex pheromone increases a female moth's willingness to mate. If the female finds a conspecific male and mates successfully, the pheromone titer reduces to save energy.