The courtship behaviour of male Spodoptera exempta (Wlk.) has been quantified and used as a method of bioassay for the female sex pheromone. Virgin females become attractive to sexually mature males from 72 hr after emergence and henceforth their attractiveness increases gradually until they have mated. Mated females start losing their attractiveness to males gradually after mating and 72–96 hr after mating they cannot produce any courtship response in males. Amongst virgin females, crude pheromone-gland extract and synthetic pheromone compounds, it is the older live females and the crude extract at 0.1 female equivalent that produce highest responses in males. A certain degree of cross-attraction between three coexisting species has been noted, both by using live insects as well as synthetic pheromone compounds of these species under laboratory bioassays. Possible interspecific pheromone-related implications are discussed.
