IMPACT OF PLASTIC BAG CONCEALMENT ON INSECT SUCCESSION PATTERNS AND DECOMPOSITION RATE OF RABBIT CARCASSES

Abstract

Insect succession on decomposing remains is widely used in estimate the post-mortem interval (PMI) in forensic investigations. However, perpetrators may conceal the body to destroy evidence and delay discovery, thereby limiting insect colonisation and altering the rate of decomposition. Despite its forensic relevance, the quantitative effects of plastic bag concealment on insect colonisation patterns, decomposition dynamics and fly developmental duration remain poorly understood, particularly under tropical conditions. This study investigated the effect of plastic bag concealment of rabbit carcasses on insect succession patterns and decomposition rate. Fifteen carcasses were divided into three groups: plastic bagenclosed indoors, plastic bag-enclosed outdoors and exposed outdoor controls across five experimental trials. Insects were collected and identified, and decomposition progression and blowfly development from oviposition to adult emergence were recorded. A total of 2005 insects were collected, predominantly Chrysomya megacephala, Chrysomya rufifacies, and Sarcophaga sp. Blowfly species Hemipyrellia ligurriens and Hypopygiopsis violacea as well as ants and carrion beetles were observed only on exposed carcasses. Exposed carcasses decomposed in approximately eight days, whereas enclosed carcasses required 18-20 days. Fly oviposition on concealed carcasses was by 28-32 hours outdoors and 49-52 indoors, and development from egg to adult emergence was significantly delayed in concealed carcasses (291–340 hours) compared to exposed controls (197-205 hours). These findings demonstrate that plastic bag concealment delays insect colonisation, decomposition, and blowfly development, emphasizing the importance of considering enclosure effects in forensic PMI estimation for concealed remains.