DNA-based and taxonomic identification of forensically important Sarcophagidae (Diptera) in southeastern Spain

Studying dipterans at the scene of a death can provide essential information for interpreting the evidence and help to reconstruct the events happened to a corpse in the past. Molecular tools have been employed for identification at specific levels in the cases of cryptic species or poorly conserved specimens. Identification of specimens is essential in forensic entomology since each species has a specific growth rate, which determines the calculation of the minimum post mortem interval (minPMI). In addition, phylogeographic reconstruction within a species can help to differentiate the haplotypes from a geographic area, thereby helping to clarify the possible relocation of a corpse. The morphological identification of Sarcophagidae species is often difficult, especially for the females. This is an important Diptera family since some of its species are among the first to reach a corpse, especially in warm areas. In this study, we compared the sarcophagids found in human corpses in forensic cases in Alicante (southeast of Spain) with specimens collected from baited traps in the same area and surrounding provinces. In total, 189 specimens were collected, comprising 72 from forensic cases and 117 from baited traps. Molecular identification was conducted by sequencing the cox1 mitochondrial gene and analyzing the sequences using ABGD, GMYC, and BIN species delimitation methods. The median joining algorithm in the PopART program was used to construct phylogeographic networks. Eight species in the family Sarcophagidae were identified. The most widely collected species were Sarcophaga argyrostoma and Sarcophaga tibialis. The haplotype networks obtained for these species did not indicate a clear geographic distribution of haplotypes. The S. argyrostoma samples from Alcoy were clearly isolated. The results demonstrated that this method is useful for identifying Sarcophagidae samples in forensic investigations and it can be employed for minPMI estimation.     

贵阳地区常见尸食性蝇类mtDNA分子标记的检测

目的应用mt DNA中COI(348bp)、COII(637bp)及16Sr DNA(513bp)基因序列鉴定贵阳地区常见尸食性蝇类的种属。方法收集贵阳地区常见尸食性蝇类标本,经形态学分类鉴定后提取胸肌DNA,扩增COI(348bp)、COII(637bp)及16Sr DNA(513bp)基因片段,测序后用DNAMAN 4.0序列分析软件进行序列拼接,NCBI中的BLAST、MEGA 5.2软件包对所得序列分析建立种内及种间进化分歧率,并构建系统发育树。结果 COI种间平均进化分歧率为12.55%,种间范围在3.0%~18.6%,种内范围在0%~0.7%;COII种间平均进化分歧率为13.73%,种间范围在5.3%~21.6%,种内范围在0%~0.6%;16Sr DNA种间平均进化分歧率为4.54%,种间范围在0.4%~7.6%,种内范围在0%~0.4%。结论 COI、COII及16Sr DNA可用于尸食性蝇类的种属鉴定,该方法可作为传统分类方法的补充手段。     

DEET (N,N‐Diethyl‐meta‐toluamide) Induced Delay of Blowfly Landing and Oviposition Rates on Treated Pig Carrion (Sus scrofa L.)

Abstract: The question of whether the insect repellent N,N‐Diethyl‐meta‐toluamide (DEET) affected fly attraction, oviposition, and larval development was investigated; in part, to determine whether the common habit of wearing DEET as a repellent could affect the rate of human decomposition. Experiments using pig surrogates of human decedents were carried out in a rural environment. Dead piglets were sprayed with DEET, and fly behavior, colonization levels, and maggot development were compared with those in nonsprayed controls. Piglets treated with DEET experienced significant delays in fly visitation and oviposition and delayed appearance of each larval instar, as well as reduced total larval numbers (p < 0.01 for all variables), with subsequently reduced decomposition (p < 0.05). Such changes in fly behavior and larval population development would significantly impact the estimation of the period following the death from entomological evidence in decedents wearing DEET at the time of their death.     

北京地区尸食性蝇类调查

目的了解北京地区目前尸食性蝇类数目及常见尸食性蝇类的季节分布。方法采用动物尸体或组织诱捕和饲养的方法采集尸食性蝇类标本,对其进行分类保存后进行观察和统计。结果北京地区尸食性蝇类为4科9亚科21属46种,其中有12种是北京新记录种。尸食性蝇类具有区域性分布和季节性分布的特性。结论北京地区尸食性蝇类及常见的尸食性蝇类季节分布数据,可为相关研究提供参考依据。     

Artifacts Caused by Leaf-Cutting Ants of the Genus Atta (Hymenoptera: Formicidae): Postmortem Bite Injuries and the Tearing of Clothes

Ants are one of the first insects to find an exposed cadaver and can be present during all stages of decomposition. Although these organisms are not commonly used in postmortem interval estimates, they are to be taken into account on criminal investigations involving human corpses, since they can leave bite marks that can be mistaken for antemortem or perimortem injuries, which could be misleading when ascertaining the occurrence of abuse or physical altercation during a crime. A few studies report the action of ants on human cadavers and even though leaf-cutting ants of the genus Atta are frequently encountered in succession studies that use animal carcasses, there are no records of these fungus-growing species on human corpses. Atta is a genus restricted to the New World, ranging from northern Argentina to southern United States and acts as one of the most conspicuous neotropical herbivores. In this study, we report three cases of violent death that illustrate the impact of ants, especially those of the genus Atta, in a forensic setting. We compare the patterns displayed by postmortem bite injuries caused by leaf-cutter ants and other common species with less robust mandibles. We also present the capability of Atta ants to create artifacts by cutting victim’s clothes in a crime scene, contributing to the knowledge of ant-mediated confounding factors in crime scene investigation.     

Species identification of some common necrophagous flies in Guangdong province,southern China based on the rDNA internal transcribed spacer 2 (ITS2)

Recent studies suggest that sequence analysis technique displays a tempting foreground in identifying unknown specimens of necrophagous flies. In this study, we analyzed 63 complete ITS2 sequences concerning 29 fly species to evaluate the identification potential of the ITS2 region, among of which 41 sequence entries were obtained by sequencing and 22 sequence entries were available on the line. Additionally, phenetic method was recommended to substitute for phylogenetic method because it is very difficult to align the ITS2 sequences. The neighbor-joining tree generated by clustalx1.81 allowed us to differentiate each species. Meanwhile the tree topology also suggested that the ITS2 region showed no resolution for the distinction of geographical populations of some species. The overlapping between intra- and interspecific variation revealed by sequence analyses did not affect species identification. High sequence homology between some congeneric species required further sequencing for forensic practice.     

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。     

A Checklist of Calliphoridae Blowflies (Insecta,Diptera) Associated with a Pig Carrion in Central Brazil*

Abstract: Although the Cerrado is the second major Brazilian biome, few studies have been undertaken about its entomofauna. Blowflies have an important role in forensic entomology, helping in the determination of postmortem intervals. The main goal of this exploratory study was to identify and to catalog the blowfly species associated with a pig carcass. The study was conducted in a pasture in Brasília, Distrito Federal. A pig (Sus scrofa) was killed with a .22 caliber shot in the frontal region of the head. Adult blowflies were surveyed daily from June 1 through 30, 2004. A total of 14,910 adult calliphorids were collected, representing eight species: Chrysomya albiceps, C. megacephala, Cochliomyia macellaria, Chloroprocta idioidea, Hemilucilia semidiaphana, H. segmentaria, Lucilia cuprina, and L. eximia. C. albiceps was the most frequent species, amounting to 94.76% of the catch. Five decomposition stages were observed, and for calliphorids, the most attractive stage was the bloated one.     

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。     

Necrophagous Caterpillars Provide Human mtDNA Evidence*

Abstract: Decomposition of large mammalian carcasses is greatly accelerated through the action of insects. Specialized feeders capable of digesting keratin and collagen found in skin, hair, and tendons and ligaments are attracted to corpses in late stages of dry decomposition and include Tinea pellionella, the casemaking clothes moth, and Tineola bisselliella, the webbing clothes moth (Lepidoptera; Tineidae). Until now, details of the caterpillar behavior as necrophagous insects were vague. Here, we detail the behavior of each species and document the incorporation of human hair into the portable larval shelters constructed by the caterpillars of T. pellionella. Hair of the decedent used as building material for caterpillar shelters provided enough starting template to amplify and sequence the HVI and HVII sections of the control region (mtDNA) of the decedent.