Abstract
Traps with sex pheromone (litlure) of Spodoptera litura were set at nine locations in five countries in Southeastern Asia to compare the daily patterns of male moths caught in traps during the overlapping two years between 1997 and 1999. When the records for observation periods were averaged, the daily number of males from June to November was low in the locations of the year-round occurrence of males, as 0.4 on Sulawesi Island in Indonesia (5°S), 2 on Luzon Island in the Philippines (15°N), 2 in Chiayi, Taiwan (24°N), 4 in Kwangsi, China (25°N), 11 in Fukien, China (27°N), and 20 in Okinawa, Japan (26°N), whereas in locations where essentially no males were caught during winter, significantly more males were caught daily as follows: 108 in Chekiang, China (30°N), 192 in Kagoshima, Japan (31.5°N) and 47 in Saga, Japan (33.5°N). This increasing tendency of males toward northern latitudes suggested the northward migration of this species, and further to Kyushu from China, distributed at the same and/or a lower latitude, if they could migrate overseas. The possible migration of this species to escape natural enemies was discussed.
