This study investigated the potential effects of Malathion in rabbit carcasses on the developmental of Chrysomya megacephala larvea, an important forensic species, and their possible implications for the calculate the postmortm interval ( PMI) .Three domestic rabbits  Oryctolagus cuniculus  were used in each experiment. Two rabbits were administered orally with 513 mg/kg (R1), 1026 mg/kg (R2) of Malathion, The third one was fed with distilled water (R0).Chrysomya megacephala larvae were allowed to grow on the liver (L), muscles (M) and all carcasses of rabbit. Malathion was detected in all collected rabbit tissues that received different dosages of Malathion (R1 and R2) but not detected in any of the controls (R₀).The highest Malathion concentration was  detected in lungs followed by muscle tissue and fats of R2(35.7 mg/kg, 29.75 mg/kg, and 22.31mg/kg, respectively). All third larval instars and pupae of C. megacephala were positive for malathion (R1 and R2), while malathion was not detected in all samples from the control colony (R0).
Strong correlations were found between administered dosage and tissue concentrations. Malathion concentrations were higher in the third larval instars sampled for the concentration (R2) than those from muscle tissues of (R2) which followed by those from L₂ colonies. Detected Malathion concentrations in the third larval instars and pupae of C. megacephala were significantly lower than those detected in the rabbit tissues except fats and heart from postmortem interval rabbit tissues treated with (R1). Moreover, the highest levels of Malathion were noticed in the pupae emerged from (R2) colony. Whereas, the lowest levels were detected in the pupae emerged from M₁ colony.