Population dynamics of the whitebacked planthopper,Sogatella furcifera (Hemiptera: Delphacidae) with special reference to the relationship between its population growth and the growth stage of rice plants
A population census was conducted to describe the effects of the growth stage of rice on the population dynamics ofS. furcifera, in particular, on immigration, seasonal abundance, population growth rate, and wing-form expression. The number of immigrants was highest on rice plants 17 to 30 days after transplanting (DAT), which suggested that immigrants prefer to settle or remain more on rice plants at the tillering stage (approximately 20–30 DAT). Population growth rate from immigration to the 1st generation decreased with an increase in rice plant age. In contrast, population growth rate from the 1st to 2nd generation was not influenced by rice plant age and was negatively density-dependent. The percentage of macropters (flyers) was positively related to the growth stage of rice when rice was in the vegetative or early part of the reproductive stage, and reached 100% at about 10 days before heading (booting stage). Threafter, most adult females molted into macropters regardless of population density. The roles of host plant age and crowding effect on the population dynamics ofS. furcifera are discussed.
Synoptic weather conditions inducing long‐distance immigration of planthoppers, Sogatella furcifera Horvath and Nilaparvata lugens Stal
1 Adults and nymphs of Sogatella furcifera and Nilaparvata lugens are serious pests of growing rice in Japan. They appear in June and July but their origin was unknown. Inflow of warm and humid air from the south was shown to favour the appearance of planthoppers. The air inflow was associated with the passage of depressions along the frontal zone, called Bai‐u in the Far East. 2 Immigrations were categorized as mass or minor according to the density of immigrants surveyed by various traps. 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 19.3 h at an average wind speed of 32.9 km/h. When the route digressed a little north or south, minor immigrations, with only S.furcifera in half the cases, occurred. 3 Minor immigration types were categorized into a long‐lasting type which appeared in the final stage of the rainy season, a mass immigration typemodified by the location of a typhoon in the south, and a minor type near the frontal line occurring without the passage of recognizable depressions. 4 The greatest aerial densities of immigrants were estimated as three to seven per 103m3 in S.furcifera and one to two per 103 m3 in N.Iugens. Female immigrants were mostly unmated. 5 All the depressions that appeared in June and July 1967–72 were analysed and twenty‐nine (76.3%) out of thirty‐eight originating in the central part of the Chinese continent, caused immigrations. Yearly fluctuations of planthopper infestations in Japan were shown to depend on the yearly fluctuations of the route of depressions associated with the migration of the planthoppers.
The Lunar Rocks
Book on lunar rocks covering pre-Apollo lunar scientific knowledge, Apollo and future lunar mission planning, lunar mineralogy, petrology and geochemistry, etc