Abstract: The lethal and growth inhibiting effects of two insect growth regulatrs (IGRs), methopreneand pyriproxyfen, on Liposcelis bostrychophila Badonnel were investigated systematicallyby feeding artificial diet containing the active ingredient. The results indicated that the two IGRshad obvious lethal action on the nymphs; and the mortalities of nymphs fed with 10 mg(a.i.)/kg diet of meth oprene and pyriproxyfen for 49 d were 80.00% and 31.11%, respectively.Them aximumnymph duration fed with 20，10，5 mg／kg pyriproxyfen were 71.0，98.2and 116.4 d, respectively,whereas that of the control was 11.3 d. Some nymphs fed on methoprene (10 mg／kg) could still develop into adults which were able to reproduce offspring. While most of the nymphs fed with pyriproxyfen at a dosage of 5 mg/kg died after 60 d, and the survivors remained in super nymphal stage. Reproduction experiment indicated that the fecundity of adults fed with methoprene(200 mg/kg) and pyriproxyfen (40 mg/kg) were 39.74% and 26.11%correspondingly, as that of the control in the first week. After 15～16 d, the hatching rates of eggs were 65.71% and 8.69%,whereas that of the control group was 93.18%. The resultssuggested that pyriproxyfen at 40 mg/kg or methopreneat 200mg/kg could effectively reducethe amount of the population of L. bostrychophila.