Factors influencing the time of the mating activity of the male of Spodoptera litura (F.) in the dusk

The number of males of Spodoptera litura (F.) taking off to fly every 10min in the dusk followed approximately a normal distribution. However, the number of individuals taking off each minute varied considerably with the wind speed. The males began to fly, on the average, 26min after sunset and the mean time of take-off was 49min after sunset. The number of males caught in the pheromone traps every 10min in the dusk also followed a normal distribution. The first catches in the trap occurred at 32min after sunset and the mean catch time was 56min after sunset. The time of take-off and catches did not vary with the month and location where the experiments were conducted. The factors influencing the changes in these times with the days of the experiments could not be detected by multiple regression analysis, using variables related to wind and weather conditions and the pheromone sources for the trap as independent variables.