Effect of citronella and chlorpyrifos on oviposition of calliphorid flies in decomposing rabbit carcasses

Abstract

The independent influences of citronella and chlorpyrifos on oviposition and duration for completing life cycles for Chrysomya megacephala and C. rufifacies on decomposing rabbit carcasses in Johor Bahru were studied in view of its application for forensic entomological assessment of postmortem interval (PMI). Twelve male rabbit carcasses were equally divided into control, citronella-treated and chlorpyrifos -treated groups and left to decompose for 14 consecutive days. Results revealed that C. megacephala was the first necrophagous fly to oviposit followed by C. rufifacies in all the control and citronella treated carcasses. The initial oviposition of C. megacephala was significantly delayed by 4-6 hours in all the citronella treated carcasses (p<0.05) although significant prolongation in the duration for completing its life cycle was not observed. In contrast, delay in the initial oviposition as well as prolongation in the duration of life cycle for C. rufifacies in citronella treated carcasses were not observed. Although delayed in oviposition was observed for the chlorpyrifos treated carcasses, the eclosion of the eggs were not successful hence rendering inability to identify the fly species that oviposited. Since forensic entomological baseline data for Johor as well as the individual influences of citronella and chlorpyrifos on oviposition and completion of life cycle for C. megacephala and C. rufifacies have not been reported, the results reported here may prove useful for estimating PMI via entomological assessment within this region, especially whenever these two chemical agents are suspected to be present.