Growth of Chrysomya megacephala (Fabricius) Maggots in a Morgue Cooler*

Abstract: In estimating the postmortem interval (PMI) using maggots obtained during autopsy, the forensic entomologist makes decisions regarding the effects of low‐temperature storage of the body on the insects. In this case report, a corpse was found in an abandoned house in the residential area of Bukit Mertajam, Penang, Malaysia. The maggots were found to be alive inside the mouth of the deceased although the corpse had been in the morgue cooler for 12 days. The maggots were reared and identified as Chrysomya megacephala (Fabricius). The emerged adult flies were kept as a stock colony, and the duration of development under the indoor fluctuating temperature regime was studied. The total duration of developmental process of this species was 9.5 ± 0.5 days, and the PMI estimated was 3.2 ± 0.6 days. This case report demonstrates the survival of Ch. megacephala maggots for 12 days and their growth inside the morgue cooler.     

四季尸食性蝇类参与尸体软组织分解过程初探

目的观察了解四季尸食性蝇类参与尸体软组织分解过程的规律。方法在室外自然环境中设置尸体,分别在春、夏、秋、冬季节,用肉眼观察尸体每一时段的变化及尸食性蝇类参与尸体分解的现象。结果在4个不同的季节中,尸体软组织分解过程中尸食性蝇类参与种类及虫态各不相同。通过观察获得尸体变化各阶段的大体历期,尸体变化各阶段常见的尸食性蝇种及虫态资料。结论观察所得资料可为推测晚期尸体的死亡时间提供参考。     

四种常见尸食性蝇类活动与产卵习性

目的　明确常见尸食性昆虫成虫的活动习性和产卵习性 ,为法医实践中死后间隔时间的判断提供借鉴 ;　方法　在自然温度、室内恒温及包括夜晚、雨天等 2 6种不同环境条件对丝光绿蝇、大头金蝇、巨尾阿利蝇、棕尾别麻蝇成虫活动与产卵 (产仔 )习性进行了观察 ;　结果　昆虫成虫的活动与产卵习性在不同环境条件下往往不同 ,不同种类之间也存在差异 ,在利用昆虫发生规律为法医实践提供死亡时间等信息时 ,应具体问题具体分析。     

Comparison of Decomposition Rates and Faunal Colonization of Carrion in Indoor and Outdoor Environments

Abstract: Decomposition and insect colonization of pig (Sus scrofa L.) carcasses were observed over a 42‐day period inside and outside a house in a suburban region of Edmonton, Alberta. Three freshly killed pig carcasses were placed outdoors on grass and three carcasses were placed in separate rooms inside a house in a suburban residential area. The carcasses were examined and sampled regularly. Outside carcasses were colonized rapidly by Calliphora vicina (R‐D), Lucilia sericata (Meigen), Lucilia illustris (Meigen), Eucalliphora latifrons (Hough), Cynomya cadaverina (R‐D), Phormia regina (Meigen), and Protophormia terraenovae (R‐D). There was a delay of 5 days before inside carcasses were first colonized but all species except E. latifrons and L. illustris readily colonized at this time. Many more insects colonized the outside carcasses, and these were rapidly skeletonized. Inside, much fewer insects were present and decomposition was slowed and colonization extended. Dispersal patterns of postfeeding larvae inside the house on hard substrate were greatly expanded compared with those from carcasses on grass.     

Maggot development during morgue storage and its effect on estimating the post-mortem interval

When insect evidence is obtained during autopsy, forensic entomologists make decisions regarding the effects of low-temperature (-1 degrees C to 4 degrees C) storage of the body and associated insects when estimating the post-mortem interval (PMI). To determine the effects of storage in a morgue cooler on the temperature of maggot masses, temperatures inside and outside of body bags containing a human cadaver and porcine cadavers (seven replicates) were measured during storage. Temperatures remained significantly higher (p<0.05) inside of the body bags relative to the cooler, and remained at levels sufficient for maggot feeding and development. If the assumption that no insect development takes place during preautopsy refrigeration is made, potential error rates in PMI estimation of 8.6-12.8% occur. The potential for blow fly larvae to undergo significant development while being stored in the morgue is a possibility that forensic entomologists should consider during an investigation involving samples collected from autopsy. Case and experimental evidence also demonstrate that substantial tissue loss can occur from maggot feeding during morgue storage.     

“尸热”现象初探

目的探讨在特定条件下尸体腐败过程中温度变化的规律,为解决死亡时间的推断提供科学依据,同时观察蝇蛆在尸体上所经历的温度变化,探寻其变化特点和规律为法医昆虫学检验提供依据。方法在深圳不同季节放置猪尸于室外的草地上,温度计探头分别置于舌下及插入直肠约5cm深处。分别观察记录口腔和直肠的温度,死亡第1d每小时测定尸体温度1次,从第2d开始每天定时测定3次。尸体上蝇类昆虫(成虫和幼虫)的发生情况逐日进行观察记录。在实验室观察恒温下不同蝇蛆滋生密度对猪肝块温度的影响。将初孵幼虫按不同密度分别接于新鲜的50g猪肝上,插入温度计,使温度计探头与猪肝块充分接触,再置于24℃的生化培养箱内饲养。在同样条件下,设立未接入初孵幼虫的猪肝块作为对照组。每天分别测定记录5次,然后对测得的结果进行统计。结果蝇蛆滋生可显著引起尸体温度上升,春季最高约上升8℃,夏季最高可上升22℃;升温主要集中在蝇蛆聚集的部位;蝇蛆滋生引起猪肝块温度上升的幅度较小,一般仅为数度;随着滋生密度的增加,升温幅度增加。结论蝇蛆活动可引起尸体温度上升,从而影响昆虫发育历期。凡有蝇蛆滋生的尸体均不能忽视"尸热现象"。     

DNA‐Based Identification of Forensically Important Lucilia (Diptera: Calliphoridae) in the Continental United States*

Abstract: Correct species identification is critical when dipteran larvae are used for inference of the postmortem interval. To facilitate DNA‐based identification of forensically important flies of the genus Lucilia in the continental United States, we develop a vouchered reference collection and DNA sequence database. A total of 122 specimens were collected for nine of the 10 species of Lucilia reported to occur in the continental United States. Using the polymerase chain reaction and DNA sequencing, data were obtained for an 1100‐bp region of the mitochondrial gene encoding cytochrome oxidase I (COI). We consider a species suitable for DNA‐based identification if it is exclusively monophyletic in >95% of bootstrap pseudoreplicate phylogenetic analyses. Seven of the nine species meet that criterion. Two species (Lucilia coeruleiviridis and Lucilia mexicana) share COI sequence and cannot be distinguished using our reference database. We conclude that DNA‐based identification is likely to be successful for the other seven species.     

根据食尸性蝇类推断死亡时间的研究进展

法医昆虫学是应用昆虫学知识解决法医实践中所遇到的相关问题的一门科学。食尸性蝇类在尸体的腐败分解中发挥着重要的作用,运用食尸性蝇类的特点可以更准确进行死亡时间推断,为侦查破案提供线索。本文对依据食尸性蝇类推断死亡时间的方法进行综述,以期为后续的研究与实践应用参考和借鉴。     

利用嗜尸性蝇类生活史推测死亡时间

目的积累一些嗜尸性蝇类生活史的资料及群落组成的季节性变动规律。方法采用动物尸体作诱饵,分别对自然飞到诱饵上繁殖生长的8种嗜尸性蝇类的生活史及群落组成的季节性变动规律进行观察研究。结果夏季高温时段蝇类群落组成物种较为丰富,冬季低温时段蝇类种群较为单一。常见8种嗜尸性蝇类虫态经历时间在气温高时较短,气温低时较长。结论嗜尸性蝇类生活史及群落组成的季节性变动规律可为推测死亡时间提供依据。     

Identification of forensically important sarcophagid flies (Diptera: Sarcophagidae) in China, based on COI and 16S rDNA gene sequences

Insects attracted to cadavers may provide important indications of the postmortem interval (PMI). However, use of the flesh flies (Diptera: Sarcophagidae) for PMI estimation is limited as the species are often not morphologically distinct, especially as immatures. In this study, 23 forensically important flesh flies were collected from 13 locations in 10 Chinese provinces. Then, a 278-bp segment of the cytochrome oxidase subunits one (COI) gene and a 289-bp segment of the 16S rDNA gene of all specimens were successfully sequenced. Phylogenetic analysis of the sequenced segments showed that all sarcophagid specimens were properly assigned into four species (Boerttcherisca peregrina [Robineau-Desvoidy, 1830], Helicophagella melanura [Meigen, 1826], Parasarcophaga albiceps [Meigen, 1826], and Parasarcophaga dux [Thompson, 1869]) with relatively strong supporting values, thus indicating that the COI and 16S rDNA regions are suitable for identification of sarcophagid species. The difference between intraspecific threshold and interspecific divergence confirmed the potential of the two regions for sarcophagid species identification.     

应用mtDNA COI基因序列鉴别常见嗜尸性蝇类种属

目的探讨mtDNA基因序列对常见嗜尸性蝇类的种属鉴别应用价值。方法收集不同区域2科4属6个种30个蝇类样本,提取样本线粒体DNA后扩增COI基因序列,以琼脂糖电泳检测扩增产物并测序,以DNAMAN6.0分析软件分别截取498bp序列,用MEGA5.2软件分别进行序列分析,然后构建系统发育树,比较各地区不同种属样本的序列差异。结果 6个种属的嗜尸性蝇类30个样本mtDNA的COI基因具有一定的序列差异,种内进化分歧均数在0.1%~1.6%之间,种间进化分歧均数在2.2%~11.2%之间,6个种属通过系统发育树均可明确区分。结论 COI基因序列分析和系统发育树对嗜尸性蝇类的种属检验具有重要帮助作用,可用于现场样本的准确、快速种属鉴定。     

NCBI数据库在常见嗜尸性蝇类种属鉴别中的应用

目的探讨NCBI数据库比对分析对常见嗜尸性蝇类种属鉴别中的应用价值。方法收集2009年1月至2012年12月重庆市常见嗜尸性蝇类不同发育历期2科5属7种样本52份,采用Chelexl00法提取mtDNA,利用2对引物扩增细胞色素C氧化酶辅酶I基因,分别截取498bp和841bp相同长度的序列,采用MEGA软件计算种内及种间进化分歧情况,并分别在NCBI数据库进行序列BLAST搜索种属同源性比对分析。结果所得序列种内进化分歧均数在0％～0．7％之间,种问进化分歧均数在7．5％～16．1％之间;7个种属的样本序列Ⅰ和序列Ⅱ分别有5个和6个种属完全比对正确,样本总体的正确率分别达到96．15％和98．08％,Maxident值均在97％以上。结论采用序列同源性比对分析,并借助NCBI数据库强大的检索分析功能,可准确进行常见嗜尸性蝇类的种属鉴定,为法医学死亡时间推断提供重要参考依据。