The objective of this study is to elucidate the effect of Pirimiphos-methyl (Organophosphorus insecticide) on protein profile of insects that found in/above or around treated rabbit (Oryctolagus cunicullus domesticus L.) carrions. Additionally, an esterase analysis was performed to clarify the effect of this insecticide on necrophagous insects. Biochemical studies were carried out on collected adult Dermestes maculatus De-Geer and pupae of Chrysomya albiceps (Weidemann) for their forensic importance. Four protein fractions observed only in the treated beetles and one unique band for the control group. Treated Chrysomya albiceps pupae exhibited 14 specific bands whereas two bands were only exhibited by the control.  Genetic distances calculated for treated and control insects were 0.38 and 0.42 for adult Dermestes maculatus and pupae of Chrysomya albiceps, respectively. Variations in protein bands may be interpreted that some pesticides enhance the transcription of certain sequences which are probably related to resistance and /or detoxification mechanisms. Esterase pattern analysis using α-naphthyl acetate reflected 4 characteristic bands for treated beetles. However, using β-naphthyl acetate yielded 4 specific bands for the control group. For Chrysomya albiceps pupae, conduction of α- naphthyl acetate yielded one common bandfor both treated and control groups and one specific band for the control group.Whereas, using of β- naphthyl acetate substrate yielded two common bands shared by both groups and one specific band for the control group. Forensically important insects such as Chrysomya albiceps Weidemann and Dermestes maculatus De-Geer have an active esterase system.