These experiments were conducted to examine the biological characteristics of Agistemus exsertus Gonzalez, a predator of tea red spider mite, Tetranychus kanzawai kishida, and to investigate the seasonal fluctuation of population density of A. exsertus. At two constant temperatures of 18 and 25℃, the developmental periods from egg to adult emergence of A. exsertus were 37.1, 12.4 days, respectively. Preoviposition periods of A. exsertus were shorter than oviposition and postoviposition periods. The numbers of eggs laid per female were 11.4 and 23.0 at the respective temperatures. The intrinsic rates of increase were estimated to be 0.032 and 0.145 ; the mean generation times were 49.8 and 18.7 days ; and the population doubling times were 21.7 and 4.8 days, respectively. The predation rate of prey eggs by all motile stages of A. exsertus was higher at 25℃ than at 18℃. The gravid female of A. exsertus was the most efficient predator stage, consuming 14.9 and 21.1 eggs of. T. kanzawai per day at 18 and 25℃, respectively. Population density of A. exsertus showed the highest peak in late June, and decreased in summer season, however, appeared the secondary peak in early October.
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