Abstract: A two-year investigation was made on the seasonal population dynamics and number of generations of the rice stem borer, Chilo suppressalis(Walker)(Lepidoptera: Pyralidaer), by use of sex pheromone trapping at two sites during 1998～1999. The results showed that the overwintering generation moths were first caught in mid May at Changchun City and to the end of May at Liuhe County in 1998. The last flight dates of moths at Changchun City were in the late and early September in 1998 and 1999, respectively. The active duration of the moths was as long as four months while one generation could complete its development(egg to egg)within two months at the location. In fact, there were two obvious peaks of moth flight at Changchun City in 1999, and the interval between the peaks was about 55 days. These indicated a high percentage of occurrence of the second generation and thereby promoted to change the long standing opinion that there was only one generation at the locations in a common year.

Key words: Soil nematode, Bioindicator, Maturity Index, Trophic group