A method for estimating density of overwintering population of the green rice leafhopper, Nephotettix cincticeps Uhler

Abstract

Censuses of population density of the overwintering generation of the green rice leafhopper, Nephotettix cincticeps Uhler were carried out in a fallow after harvest of rice plants from early January to early April in 1968 and 1969 at an interval of about two weeks. Aggregation pattern of this insect in the field was examined by using the method of regression analysis of the two popu lation parameters, viz. "mean density (x)" and the Lloyd (1967)'s "mean crowding (X)", which was proposed by Iwao (1968). A linear regression, X=0.24+1.71x, was established with a high degree of fitness (r²=0.98), which meant that a stable pattern of an overdispersed distribution was prevailed in the field. It was indicated that 20-40 samples (each sample covers insects within a circle of 30 cm in diameter) assured the relative precision (sx/x) of 0.20-0.30 or less in a wide range of mean densities. Some characteristic features of the distribution pattern in the fallow were also mentioned in relation to that in the paddy field.