Relationship between Wing-Form Response to Nymphal Density and Black Colouration of Adult Body in the Brown Planthopper, Nilaparvata lugens (Homoptera:Delphacidae)

During successive selection for adults with a special wing form from a population of the brown planthopper, Nilaparavata lugens, a negative correlation was found between the proportion of brachypters and the grade of black pigmentation in the adults : population including more blackish individuals tended to exhibit a lower ratio of brachypters. The selection for blackish macropters finally generated a population producing predominantly macropters, while the selection for yellowish brown brachypters produced a population exhibiting totally branchypters, over broad ranges of nymphal densities in both sexes. Two populations from Malaysia and the Philippines were quite similar to this brachypter producing population in their wing-from responses to density. All of 14 populations collected in Saga and Nagasaki Prefectures during 1986 and 1987 were highly macropterous and their body coloues were blackish. During these two years, population density of the immigrants in paddy fields was unusually high inthe rainy season in both prefectures, but the insects did not cause severe damage to rice plants in most districts. Whether these unexpected enects were due to the immigration of hoppers with highly macropterous character was discussed.