The failure of insecticides to control pests is becoming more serious around the world.One of the consequences of this failure is that more insecticides are retained in soil,run-off water,and foods as persistent organic pollutants,resulting in severe environmental pollution.So elucidating the pesticide metabolic process of insects has a huge significance.Fenvalerate,a widely used synthetic pyrethroid pesticide that is effective in controlling insect populations,has encountered the rapid development of resistance [1-3].The cabbage looper (Trichoplusia ni,Tn) is a common crucifer pest that has exhibited resistance to the pyrcthroid insecticides.In our previous study [4],three P450 monooxygenase isozymes that were functionally connected with the hydroxylation reaction in Tn cells were identified in the fenvalerate challenge process.This finding suggested that the P450 might increase the hydrophilicity of fenvalerate by modifying its chemical groups.In the present study,we attempted to examine the chemical structure modification of fenvalerate after it has been metabolized in Tn cells,which will help us identify the molecular metabolic basis of the insecticides action inside the living cells.