2004 Volume 39 Issue 1 Pages 119-125
Seasonal occurrences of the diamond-back moth (DBM), Plutella xylostella were investigated on Ishigaki-jima Island, the southernmost part of the Southwest Islands of Japan. The number of DBM captured on Ishigaki-jima Island was relatively high from October to the subsequent May every year in the presence of a sufficient amount of cabbages; however, the number was very low or zero during summer, probably because the host plant was scarce and/or the air temperature was too high. Just after the passing of a typhoon near Ishigaki-jima Island in October 1998, sudden trap catches of DBM were observed, which is assumed to be based on immigration via air currents associated with the typhoon. Since many temperate exotic butterflies were collected on and near Ishigaki-jima Island at the same period, the sudden increase of the trap catch of DBM at that time is assumed to indicate that these DBM have the same regional origin as those butterflies, which was assumed to be central China or more northern areas. The impact of the migration of DBM associated with the typhoon on their population increase on Ishigaki-jima Island, however, did not appear to be significant.
