Abstract:Theocolax elegans (West.) is a predominant parasitoid of Sitophilus oryzae (L.) in South China. In order to the conservation and utilization of this wasp, laboratory studies were conducted to assess the population dynamics of them and effectiveness of the long-winged parasitoid wasps, T.elegans for suppressing populations of S.oryzae using methods for single element variance analysis and LSD multiple comparisons. The population dynamics of T.elegans and S.oryzae showed that the developmental duration of them for one generation were 25 days and 40 days respectively at 25℃, 65% RH. The control experiment revealed that the released female wasps at different density of 1, 2, 4, 8, 16, 32, 64 and 128 per box all can colonize and play an important natural control effect on rice weevil. When 64 female adults of T.elegans were inoculated in wheat, which the ratio between wasps and rice weevil was 1 to 6, the control effectiveness is the best, and the control effectiveness could reach 89.11%-96.47% after 10 to 50 days from initial wasp release, which show significant difference from the others. These results suggested that T.elegans could effectively control the occurrence and damage of S.oryzae under laboratory condition.