A Study on Forensically Important Insects and the Influence of Environment Factors on Rabbit Carcasses Treated with Formic Acid

Mohd Khalil, Jusoh (2019) A Study on Forensically Important Insects and the Influence of Environment Factors on Rabbit Carcasses Treated with Formic Acid. Masters thesis, Universiti Malaysia Sarawak.

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Abstract

Post mortem interval can be estimated based on the succession pattern of forensically important insects. There are various factors that may influence insect succession and decomposition process. One of the factor is the presence of chemical on dead body compound that may interfere with the insect colonisation thus under-determined the post mortem interval. This study was to look into the effect of formic acid treated-rabbit carcasses on the decomposition process and the succession pattern of the necrophagous insect at the Endap oil palm plantation, Samarahan, Sarawak. The study was carried out in three trials of experiment. Each trial consists of one untreated rabbit carcasses (control) and two rabbit carcasses poured with formic acid. The control rabbit carcasses and treatment 1 (T1) rabbit carcasses were put in an open area while treatment 2 (T2) rabbit carcasses were put in shaded area. The decomposition process and insect succession pattern of different treatment on rabbit carcasses were recorded and compared in all three trials of experiment. From this study, a total of 1,163 of insects were collected from three trials of experiment conducted in year 2016. A total of three orders namely Diptera, Hymenoptera and Coleoptera were collected. There were four families identified in order of Diptera, while the insects under the order of Hymenoptera and Coleoptera were unidentified. The most predominant species collected at the study site is a dipteran flies, Chrysomya rufifacies (33.01%) and followed by Hemipyrellia ligurriens (32.49%). The treated and untreated carcasses have shown five stages of decomposition process; fresh, bloated, active decay, advanced decay and dry remain. The decomposition of formic acid treated rabbit carcasses took around 13 to 14 days to complete compared to the untreated carcasses which only took 7 days to complete. From the field observation, the insects’ arrival was delayed for 24 hours for treated carcasses and there were some larvae that did not develop into adult and died on the carcasses. The mean ambient temperature was ranged from 24.5 to 30.4 ⁰C, with 83-85% of relative humidity. Throughout this study the highest rainfall recorded was 67.6 mm. The environment parameters did not influence the insect succession pattern of the untreated and treated rabbit carcasses. To conclude, the formic acid treated on the carcasses has interfered with the insect arrival time and period of decomposition process. The information on the effect of formic acid on carcasses may assists forensic entomologist to accurately estimate the post mortem interval time in the future where formic acid is involved. Keywords: Forensic entomology, Chrysomya rufifacies, Hemipyrellia ligurriens, decomposition, insect succession, formic acid

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