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

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±20 h进入白骨化期,而冬季则时间较长,约经过1 297±63 h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。     

杭州地区猪尸体上昆虫群落的组成与演替的初步观察

对杭州地区猪尸体的腐败过程及尸体上昆虫群落的演替规律,进行了初步观察和研究。结果表明,室外地表上猪尸体的腐败过程可以划分为新鲜、肿胀、腐烂、干化和残骸5个连续的阶段;常见昆虫包括3目、19科、33种,其中双翅目的巨尾阿丽蝇、丝光绿蝇、南岭绿蝇、大头金蝇、肥须亚麻蝇等为优势种。尸体上昆虫群落的演替有明显的时间规律可循。许多昆虫类群的出现时间与尸体腐败阶段有明确的对应关系,这种对应关系可以为法医科学中推测死后间隔时间(postmortem interval, PMI)提供依据。     

Social wasps (Vespidae: Polistinae) on carcasses of Rattus norvegicus (Mammalia: Muridae) in the Central Amazonia,Brazil: possible forensic implications

We evaluated the occurrence of social wasps in the decomposition process in tropical rainforest in central Amazonia (Ducke Reserve, Manaus, Brazil), using cadavers of rats as attractants, exposed in suspended cages. Ten species, in three genera, of social wasps were collected only in the initial stages of decay (fresh and bloated). Five species were collected, mainly in the fresh stage, feeding on flesh: Agelaia angulata, Agelaia constructor, Agelaia fulvofasciata, Agelaia pallipes and Angiopolybia pallens. Five species were collected, mainly in the bloated stage, feeding on flesh and eggs and first instar larvae of dipteran: Agelaia testacea, Angiopolybia obidensis, Apoica arborea, Apoica pallens and Apoica thoracica. Due to the aspect of the injuries caused by the wasps to the carcass, they may be mistaken as skin ulcers, burns or abrasions, which may mislead a forensic investigation.     

Seasonality of insect succession on exposed rabbit carrion in Guangzhou, China

Abstract  Succession patterns for insect fauna, spanning four seasons, on rabbit carcasses were studied in Guangzhou China from 2006 to 2008. A total of 49 taxa belonging to three orders and 15 families were collected and identified. Four decomposition stages were recognized: fresh, bloated, decay and dry stage. Taxa diversity was higher in bloated and decay stages than fresh and dry stages. Internal and ambient temperatures were measured. Maximum internal temperature arrived earlier in warmer seasons. The sequence of insect succession in this study follows the same general patterns: the Diptera peaked initially, and the Coleoptera peaked later. Chrysomya megacephala was the dominant species in four seasons. Its time point of different development stages on carrion could be the most important indicators for PMI (postmortem interval) estimation in Guangzhou. Yearly and seasonal differences in activities of insects were compared. Alpha diversity indices were calculated. There were no significant differences in Shannon-Wiener index, evenness ( J ) and dominance ( C ) between seasons and years. From the Jaccard similarity index, the highest similarity was between winter and spring, while the lowest was between summer and winter. Some species occurring exclusively in one season may be important to characterize different seasons. A list of the insect taxa associated with above-ground rabbit carrion during the four seasons was compiled, which can be used for estimating time since death in similar bio-climate areas.     

Forensic entomology: a new hypothesis for the chronological succession pattern of necrophagous insect on human corpses

Forensic entomology can help to estimate the time elapsed since death, by studying the necrophagous species collected on a cadaver and its surroundings. The determination of the so- called post mortem interval (PMI or period of first oviposition) is based on the development time of necrophagous dipterans and on the chronological pattern of insects’ succession on the corpse throughout the decaying process. In the present study, authors investigated this succession by the analysis of the database of the Department of Forensic Entomology of the French Gendarmerie over 12 years (1992–2003) in order to propose a new approach and a new hypothsesis of the dynamic of necrophagous-insects’ populations present on a human cadaver over time. For all treated cases, the presence/absence and the oldest development stage of the species were recorded. Data were analyzed by statistical and Wagner parsimony methods. The statistic results allowed the association of groups of species with typical developmental stages. The Wagner parsimony analysis showed that the dynamic of the necrophagous insect population present on a cadaver could be characterised by specific species. Together, they allowed establishing hypotheses of succession of necrophagous insects on human cadavers over time that could be usefull in the PMI estimation.     

北美法医昆虫学年会及其论文简介

北美法医昆虫学第1,2届年会于2003年8月7～9日和2004年7月21～24日分别在美国内华达州拉斯维加斯和加利福尼亚州戴维斯召开,大会论文涉及到了案例分析、分类鉴定、教学、死后间隔时间推断和死亡原因查找等诸多方面。文章介绍了北美法医昆虫学年会,并对北美法医昆虫学第1,2届年会论文的相关内容进行总结分析。     

我国嗜尸性蝇类的鉴别、发育及演替研究现状与分析

嗜尸性蝇类是法医昆虫学调查中最重要的目标,作为早期到达尸体并主要促成尸体组织腐解的昆虫,对死亡时间的推断,特别是腐败尸体死亡时间的推断具有重大意义。本文针对我国嗜尸性蝇类的主要种类及形态识别、各种类生长发育、在尸体上的演替进行了综述。     

巴西东南部夏、冬季吹蝇幼虫的食后扩散

估计死亡和案发之间的最短时间是法医昆虫学的重要目标之一。在估计死亡时间时,研究吹蝇扩散至关重要。如果低估了最早扩散的幼虫距离和深度就可能低估死亡的时间。因此,掌握影响吹蝇幼虫扩散的有关因素,包括竞争、同类相食、在食源上的聚集密度、光周期、温湿度等以及潜入习性,进而推测吹蝇幼虫在尸体附近或远离尸体化蛹等都会影响估计死亡时间的准确性。本研究分析了从2006年夏季至2007年冬季在巴西南部自然状态下吹蝇食后的扩散。除趋光性外,扩散距离在季节上的不同(夏季3·1 m对应冬季的1·2 m)是由于环境条件起了重要作用。在用屠宰动物模拟实验时显示,吹蝇幼虫在低温低湿环境下扩散的时间滞后,扩散的距离也缩短。本研究表明温度(也许包括湿度)影响吹蝇幼虫的扩散,环境条件也决定吹蝇何时开始扩散。     

Characterization of the complete mitochondrial genome of Hydrotaea spinigera (Diptera: Muscidae) with phylogenetic implications

Hydrotaea spinigera Stein is a muscid species with high forensic importance. To further supplement the genome-level features of related species, the complete mitochondrial genome of H. spinigera is amplified, sequenced, annotated, analyzed, and compared with 13 other species of the family Muscidae. This mitogenome is 15,517?bp in length, with a standard set of 13 protein-coding genes (PCGs), 22 transfer RNA (tRNA) genes, two ribosomal RNA (rRNA) genes, and a typical non-coding control region. The gene organization, base composition, and secondary structures of tRNA genes of this mitogenome are similar to other dipteran species. Phylogenetic analyses based on all the mitochondrial PCGs and rRNA genes for 14 muscid and one outgroup taxa are performed using Bayesian inference (BI) and maximum likelihood (ML) analysis. The inferred trees indicate that the Muscidae, the subfamily Muscinae, and the tribes Azeliini and Reinwardtiini are monophyletic, whereas the monophyly of the subfamily Azeliinae and the tribe Muscini is not supported.     

Utility of GenBank and the Barcode of Life Data Systems (BOLD) for the identification of forensically important Diptera from Belgium and France

Fly larvae living on dead corpses can be used to estimate post-mortem intervals. The identification of these flies is decisive in forensic casework and can be facilitated by using DNA barcodes provided that a representative and comprehensive reference library of DNA barcodes is available.We constructed a local (Belgium and France) reference library of 85 sequences of the COI DNA barcode fragment (mitochondrial cytochrome c oxidase subunit I gene), from 16 fly species of forensic interest (Calliphoridae, Muscidae, Fanniidae). This library was then used to evaluate the ability of two public libraries (GenBank and the Barcode of Life Data Systems – BOLD) to identify specimens from Belgian and French forensic cases. The public libraries indeed allow a correct identification of most specimens. Yet, some of the identifications remain ambiguous and some forensically important fly species are not, or insufficiently, represented in the reference libraries. Several search options offered by GenBank and BOLD can be used to further improve the identifications obtained from both libraries using DNA barcodes.     

Effect of body length and temperature on the crawling speed of Protophormia terraenovae larvae (Robineau-Desvoidy) (Diptera Calliphoridae)

This work investigates variation in the crawling speed of Protophormia terraenovae larvae (Robineau-Desvoidy) (Diptera Calliphoridae) as a function of body length and ambient temperature. A video-tracking system was used to follow the movement of larvae in an experimental arena, and to estimate their average crawling speed. Recordings were carried out at various temperatures using larvae of different developmental stages. As temperature increased, the larvae crawled at a faster speed. Furthermore, speed increased as a function of body length. We present a general allometric relationship to express the average crawling speed of larvae as a combined function of temperature and body length, expressed in the following equation: speed (cm/min)=5.45 x log[length (mm)]+0.66 x temperature (degrees C)-12.8. These results are particularly useful in forensic entomology for estimating the time that elapsed following the larva's departure from the corpse. This information can provide more accuracy for post-mortem interval estimations and a better comprehension of larvae behaviour and displacement.