In this paper, the log-series model for studying species-abundance distrib-tions of pest-natural enemy communities in paddy fields is discussed. Ecological efficiencies of several diversity indices are compared too.The log-series model is the ideal one which describes the species abundance distributions in the pest-natural enemy community in paddy fields. Analyzed data show that those two communities which follow a single log-series distribution respectively could be enlarged or mixed into a community which...