Mating behaviour and fecundity of the red bollworm Diparopsis castanea Hmps. (Lepidoptera Noctuidae)

Abstract

Experiments in Malawi showed that the (log) number of males of Diparopsis castanea Hmps. attracted to sex pheromone traps was linearly related to the (log) number of virgin females used as attractant. Virgins remained sexually attractive for up to 31 days but were maximally attractive three nights following emergence; 97·7% of light-trapped females were mated, a small proportion having mated four times. Numbers of matings were directly correlated with temperature at 22.00 h, but relative humidity had little effect. Mean fecundity of mated females was 152 ± 10·3 eggs, multiple mating influencing egg fertility rather than total oviposition. Potential fecundity was linearly related to body weight on emergence. Peak oviposition of unfertilised eggs by virgins occurred at about nine nights following emergence. Of emerging females 2% were barren. Only 1·4% of females mated twice in one night when confined outdoors with males, and there was no difference in the abilities of newly emerged males or males up to four days old to mate with newly emerged females or females up to four days old. Although outdoors males mated on average 0·8 times per night throughout their life, and were capable of mating twice per night, mating propensity of males under laboratory conditions was much lower. Males responded to female sex pheromone throughout the calling period of the female, individuals completing up to 143 orientations during a night without the occurrence of lasting physiological habituation to the pheromone. The importance of this in any control programme aimed at disrupting pheromone communication between the sexes is discussed.