Abstract
The effects of illumination intensity and temperature on female calling behaviour and male sexual response of the rice stem borer moth, Chilo suppressalis WALKER, were investigated. The critical illumination intensity for calling initiation varied with temperature. At a high temperature of 30°C, calling was inhibited by a feeble light greater than 40 lux, but the critical illumination intensity for calling initiation shifted higher with decreasing temperature. Also, calling was initiated by decrease of temperature from 25°C to 15°C under 500 lux, over the critical illumination intensity at 25°C, without light-off stimulation. This phenomenon seems to corroborate the phenomenon that the critical illumination intensity for calling initiation varies with temperature. The critical illumination intensity for male sexual response to the female sex pheromone extracts also varied with temperature, and it coincided more or less with that of mating initiation. Therefore, it seems that the critical illumination intensity for mating may be attributable in part to that of male pheromone-responsiveness at each temperature. These results suggest that one of the reasons for the seasonal variation in the mating time of Chilo suppressalis is attributed to the changing sensitivity of moths of both sexes to light according to the temperatures to which they are exposed.
