珠江三角洲猪尸体上昆虫群落的演替及其对法医学中死亡时间推断的指示意义

Succession and development of insects on pig carcasses and their significances in estimating PMI in the Pearl River Delta region

为了解决刑事案件中死者死亡时间推断的难题,不同季节野外环境用18头猪尸体做模拟材料观察和筛选对推断死亡时间高度准确的昆虫指标。结果表明,幼虫开始出现时间、幼虫开始爬离时间、大部分幼虫爬离尸体的时间、开始化蛹的时间、大部分幼虫化蛹的时间、开始羽化的时间、羽化结束的时间等若干昆虫指标比较敏感且稳定可用作死亡时间的精确推断。在珠江三角洲春季、夏季及秋季尸体腐败很快,分别在259±23,202±18,277±20h进入白骨化期,而冬季则时间较长,约经过1297±63h才进入白骨化期。大约有47种嗜尸性昆虫在尸体生态环境出现,大多数种类全年可见,尸体上的昆虫群落的优势种为大头金蝇Chrysomya megacephala、绯颜裸金蝇Achoetandrus rufifacies及厚环黑蝇Hydrotaea(Ophyra)spinigera。蝇类昆虫在尸体上只能大规模繁殖一代尸体即白骨化。根据以上结果可确定一些可用于死亡时间推断的关键时间点。

In order to solve the difficulty of the determination of postmortem interval （PMI） in criminal cases,18 pig carcasses were placed in outdoor environment in different seasons to observe and select the critical entomological index in accurately estimating of PMI. The results showed that these indexes, including T1 （larvae begin to appear）, T2 （larvae begin to crawl away）, T3 （most of the larvae have crawled away）, T4 （larvae begin to pupate）, T5 （most larvae have pupated）, T6 （pupae begin eclosion） and T7 （the end of eclosion）, could be used as accurate PMI indicators for their high sensitivity and stability. The carcasses decayed very quickly in spring, summer and autumn, and it took 202 ± 23 h, 202 ± 18 h, 277 ± 20 h for test carcasses to decay from fresh to skeleton in these seasons, respectively. In winter it took a longer time of 1 297 ± 63 h to decay from fesh to skeleton. About 47 insect species were found on carcasses. Most of the necrophagous insects could be found all the year, and there was no marked difference in species composition among the four seasons. The predominant species were very apparent. The fly larvae included mainly Chrysomya megacephala, Achoetandrus rufifacies and Hydrotaea （Ophyra） spinigera. The necrophagous insects could only breed one generation on carcasses before the carcasses become into skeleton in most of the time. Based on these results, critical time points for PMI estimation could be determined.