Determination of malathion levels and its effect on the development of Chrysomya megacephala (Fabricius) in South China.

The present study determines the concentration of Malathion in rabbit tissues and Dipteral larvae feeding on those tissues. Malathion was found in all muscle and liver samples of the test rabbit, as well as larvae fed on it. Samples from the control rabbit and pupae from all colonies were negative for Malathion. Correlations were found between administered dosage, tissue concentrations and younger or prepuparial larvae. Effects of Malathion on the development rate of Chrysomya megacephala (Fabricius) were also reported. C. megacephala is the most common fly species found on corpses in South China during the early stages of decomposition. Significant differences in larval growth rate were both observed among the colonies fed on muscle and liver. The presence of Malathion in both muscle and liver appears to retard the normal growth rate of C. megacephala in larval stage. Larvae from all colonies fed on tissues from rabbits treated with Malathion were smaller and attained maximum length later than those from the control colony. Duration of the larval and pupal stages was both significantly prolonged for larvae on tissues from rabbit receiving Malathion than those from the control colony. The difference of the duration of the larval and pupal stages together from the muscle colonies would alter the postmortem interval estimation by up to 36h. As for liver colonies, it would alter the postmortem interval estimation by up to 28h. A significantly different duration of the larval and pupal stages from the muscle colonies would alter a postmortem estimate by up to 28h relative to the liver colonies.