Estimation of population productivity of Parapleurus alliaceus Germar (Orthoptera: Acridiidae) on a Miscanthus sinensis Anders. grassland : I. Estimation of population parameters.

To assess the population productivity of the grasshopper Parapleurus alliaceus Germar in a Miscanthus sinensis Anders. grassland, estimates of population density, survival, and dilution rates were attempted using the mark-release-recapture method. No significant departure from the random-catch hypothesis, which is the basic pre-requisite for the estimation of population parameters, was discovered. A comparison between the results of two experiments, attempted simultaneously in the same area of the grassland, indicated that the accuracy of the mark-release-recapture method was acceptable for our purpose. The population trends in 1968 and 1969 showed that mortality during the early nymphal instars was remarkably low (75% and 62%, respectively, for the period from the second instar nymph to adult), and that adult longevity was greater than 10 days. The number of nymphs hatched in 1969 was smaller than 1968, and the cause of this reduction was thought to be the predation of eggs during autumn and winter.