A comparative analysis on the distribution of nymphal populations of some leaf- and planthoppers on rice plant

Summary The frequency distribution of the number of nymphs per hill of rice plant were analyzed for three species of rice leaf- and planthoppers,Nilaparvata lugens, Delphacodes striatella and Nephotettix cincticeps, based on the sampling data obtained during their last generations in the paddy field. For every species concerned, individual distributions were proved to be contagious and to fit well to the negative binomial distribution. Further, it was found that the value of negative binomial parameterk is so stable for same species that a single value ofk is applicable for a series of counts with different means, whereas thatk differs remarkably among different species: if the reciprocal of the weighted estimate of commonk which is an adequate index measuring degree of contagiousness of the distribution, is compared among different species, it is higher in the order ofNilaparvata, Delphacodes andNephotettix. The ecological and practical implication of constancy and heterogeneity within and among species was discussed respectively as to the value of parameterk.