DIEL RHYTHMS OF CALLING BEHAVIOR AND PHEROMONE PRODUCTION OF ORIENTAL TOBACCO BUDWORM MOTH, HELICOVERPA-ASSULTA (LEPIDORPTERA, NOCTUIDAE)

Both calling behavior and titer of(Z)-9-hexadecenal (Z9-16:Al), the major sex pheromone component of Helicoverpa assulta, in pheromone glands showed distinct diel periodicity, and these two were synchronous. Calling was most actively performed and the pheromone titer reached a maximum from 2 to 6 h after lights-off. During photophase, no calling was shown and only a relatively small amount of Z9-16:Al was detected. However, there was a time lag of a few days between peak calling activity and maximum pheromone titer. The pheromone titer was maximal from age 1 day to age 5 days and thereafter decreased while calling was most actively performed after age 3 days. Titers of three minor components, hexadecenal, (Z)-11-hexadecenal, and (Z)-9-hexadecenyl acetate, showed similar daily fluctuation patterns to that of Z9-16:Al, but relative to the titer of Z9-16:Al, the titer of the two aldehyde components remained relatively constant whereas that of Z9-16:Ac increased in the late scotophase.