| Research Abstract |
We have proposed that the common cutworm, Spodoptera litura immigrates to Japan from overseas by the aid of typhoon, by comparing the patterns of daily catch of male adults by pheromone traps set at Saga and Kagoshima in Kyusyu. In this research, we set the traps also at Okinawa and Ishigaki in South West Islands distributing at more than 500km distance from Kyusyu, and found that the males were caught suddenly and simultaneously not only at the time of typhoon approach, but also at the time of heavy rainfalls in Kagoshima, Okinawa and Ishigaki during early summer rainy season, and in Saga and Kagoshiam during autumn rainy season. These results support the immigration of this months from overseas also by the aid of winds relevant to rainy front. We further checked the traps set in Indonesia, Philippines, Taiwan and three places in China. Unexpectedly, far smaller number of males were caught in Indonesia, Philippines, Taiwan than those caught in Japan. I visited Taiwan twice during this research and found low capacity of the pheromone to attract the males, even though the larvae were commonly found in the fields, suggesting the presence of geographical variation, which differs in sensitivity to pheromone. The patterns of daily record of male catch were considerably similar among Saga, Kagoshima and south-east China, supporting migration origin in south-east China. We demonstrated that the moths can fly more than 20 hours by tethered flight, and utilize triacylglycerol as flight energy source.
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