Neural inactivation of sex pheromone production in mated lightbrown apple moths, Epiphyas postvittana (Walker)

Abstract

Activation of sex pheromone production in virgin female moths has been intensively studied over the last few years. In contrast, little is known about the reciprocal process, inactivation of pheromone production in mated females. In females of the lightbrown apple moth, Epiphyas postvittana, mating results in the permannent inactivation of pheromone production. Injection of mated female haemolymph or extracts of male accessory glands or whole reproductive tracts into virgins failed to induce this effect, suggesting that whatever elicits the inactivation is not transported humourally. When pairs were artificially forced apart during copulation, females without a spermatophore in their bursa copulatrix all produced levels of pheromone similar to virgins, while of the remales with a spermatophore in their bursa copulatrix, 47% produced levels similar to virgins and the remainder produced levels similar to mated females. This suggests that mechanical factors are not responsible for inducing inactivation of pheromone production. However, when the ventral nerve cord of females was transected before mating, the resultant mated females produced levels of pheromone similar to virgins, indicating that inactivation of pheromone production is induced by a neural signal, originating from the abdomen, which travels up the ventral nerve cord to a higher centre. Data are presented to support the hypothesis that the signal functions by switching off the release of pheromone biosynthesis-activating neuropeptide, or a like neuropeptide from the corpora cardiaca.