Abstract:The toxicity of 8 kinds of insecticides to 1st and 3rd instars of Delia antiqua larvae was detected using the dripping ration liquid and dipping methods. Effects to development and adult fecundity of D.antique were studied by treating the 1st and 3rd larvae of onion maggot with LC30-40 concentration of clothianidin, thiamethoxam and other insecticides. The field experiments were also treated. The results showed that LC50 of clothianidin and thiamethoxam to the 3rd instar larvae was 14.7839 mg/L and 13.3055mg/L, it is only 0.41 and 0.50 times those of chlorpyrifos, respectively. When the 3rd instars were treated by LC30-40 concentration, compared to control, surviving larvae weight reduced by 35.47% and 36.34% at six days treated, larval developmental period prolonged 3.68 and 3.98 days, pupation rate reduced by 71.91% and 78.65%, female pupae weight decreased by 13.36% and 14.72%, male pupae weight decreased by 15.97% and 18.32%, emergence rate reduced by 12.50% and 17.86%, eggs laid per female reduced by 47.71% and 51.68% respectively, and it showed that clothianidin and thiamethoxam had obviously adverse effects on development and adult fecundity of surviving 3rd larvae. The clothianidin and thiamethoxam had obviously adverse effects on development and adult fecundity of surviving 1st larvae. The clothianidin and thiamethoxam have excellent effectiveness to the larvae of D.antiqua. The control effect to the larvae reached 98.16% and 92.46% in 7 days treated with 1 200 g/hm2 dose of clothianidin and thiamethoxam, respectively. Therefore, they are worth to be extending and applying in the fields.