Since Murata (1927) failed to find overwintering populations of the brown planthopper, Nilaparvata lugens Stál and the white-backed planthopper, Sogatella furcifera Horváth during a three year survey in 1920-23, several entomologists have suggested that the two planthoppers may immigrate from far-distant sources. However, most workers have insisted that the insects overwinter on weeds in unknown habitats, although none had been found. In 1967, Tsuruoka made an important observation on the weather ship ‘Ojika’ at the ocean weather station ‘Tango’ 29°N and 135°E, about 500km south of mainland Japan where a mass of planthoppers were seen flying into lights or flying in daylight around the ship (Tsuruoka,1967).
Flying planthoppers have been surveyed in 1967-72 at Chikugo, Fukuoka, thrcughout the immigration period and meterological factors, particularly those accompanied with the passage of depressious along the frontal zone in the rainy season, in the temperate Far East called Bai-u, were analysed and categorized. The mass immigrations were induced by the passage of depressions which emerged in the central part of the Chinese continent between 25°N and 35°N and proceeded eastwards between the observation point and about 600 km north. Warm and humid south west winds blew, on average, for 19.3h at an average wind speed of 32.9km/h. When the route digressed a little north or south, minor immigrations, with only S. furcifera in half the cases, occurred. Minor immigration types were categorized into a long-lasting type which appeared in the final stage of the rainy season, a mass immigration type modified by a location of a typhoon in the south, and a minor type near the frontal line occurring without the passage of recognizable depressions.
Since 1969 intensive surveys have been carried out on a cruising Fishery Investigation Ship or Weather Ship at a station located at 3l°N and 126°E or 127°E on the East China Sea over which migrants are supposed to travel during late June to early July, the later period of the rainy season. In most cases, routine surveys were made in catching flying insects by 3 tow nets, 1 m in diameter and 1.7m deep set on the main mast, in addition to light traps and sweeping with insect net.
A large number of small insect species were included in the catches among which the planthoppers predominated in this season accounting for more than 90% of the total numbers in the catches. Among the planthoppers, S.furcifera accounted for 50 to 70% of the total , N.lugens for 50 to 30% , and Laodelphax striatellus Fallén for 10 to 15%. Sogatella panicicola Ishihara, Metadelphax propinqua Fieber were consistenly observed, white Nilaparvate miuiri China and Sogatella longifurcifera Esaki et Ishihara were sporadically observed.
The author issued an hypothesis of long-distance migration of the two species of planthoppers covering East and South-East Asia. Year round breeding of the two species is only possible in the tropics and there would be some possibility of northwards migration as the first step to the Chinese continent through the tropical frontal system prevailing from March to April.
雑誌名
三重大學農學部學術報告 = The bulletin of the Faculty of Agriculture, Mie University
ウンカ類の長距離移動 <特別寄稿>
AN002343370006702.pdf
(1.02MB)
