温度对4种常见尸食性蝇类生长发育的影响及其法医学意义

为查明温度对尸食性蝇类生长发育的影响，便于推断死亡时间，在实验室恒温条件下，以常见的4种尸食性蝇类，即巨尾阿丽蝇Aldrichinagrahami、丝光鲜蝇Luciliasericata、大头金蝇Chrysomyamegacephala和肥须亚麻蝇Parasarcophagacrassipalpis为材料进行研究。结果表明，在实验温度范围内，除巨尾阿丽蝇二、三龄幼虫和丝光绿蝇三龄幼虫之外，各种类各发育阶段的历期均随温度增高而缩短，巨尾阿丽蝇蛹在12℃和30℃时停止发育。根据试验结果，利用线性回归方程对发育速率与温度间的关系进行了模拟，结果均有良好的相关性。研究结果具有推断死亡时间的法医学意义。     

棕尾别麻蝇的季节分布及虫态变化与死亡时间的研究

目的提供法医学死亡时间鉴定的准确性.方法在海拔1115.2～¨20.8m处每月投放一次诱饵,一天观察两次并详细记录,对嗜尸蝇类季节分布进行1年的调查研究.发现棕尾别麻蝇只在8、9、10三个月份繁殖后代而且虫态变化历期也出现明显差异.特别是10月份幼虫进入蛹期后发育历期持续到次年4月份才羽化出蝇,整个发育历期长达半年之久.结果这种有季节性分布的蝇类及特定季节发育历期延长的特点,对法医学推断死亡时间及对其它嗜尸蝇类的研究均有参考价值.     

贵阳市郊嗜尸蝇类群落组成及生长观察

目的观察嗜尸蝇类种群落组成、季节变动及蛆虫生长长度与死亡时间的关系，为在死亡时间推断中应用提供基础数据。方法采用荷兰猪尸／兔尸／猪肺作诱饵，在海拔1115．2～1120．8m的自然环境中吸引蝇种。捕抓特定时间段内优势蝇种，每日定时观察记录其在营养基上产卵、幼虫孵化、成熟幼虫爬离的时间，测量其长度，采用Excel软件进行数据处理。结果获取了贵阳市郊宽丽蝇、巨尾阿丽蝇、紫绿蝇、丝光绿蝇、棕尾别麻蝇、肥躯金蝇、大头金蝇和绯颜裸金蝇等8种常见嗜尸蝇类群落组成、季节变动及蛆虫生长长度的规律性变化数据，并用于实际案例死亡时问的推断。结论嗜尸蝇类群落组成、季节变动及蛆虫生长长度在推测死亡时间上有重要意义。     

潍坊地区六种常见嗜尸性蝇类mtDNA COI区序列研究

目的解决蝇类成虫、蛹和蛆快速、准确鉴定的难题。方法随机采集潍坊地区人尸周围环境中的蝇类成虫、蛹和蛆,提取其mtDNA,经PCR扩增、产物检测与纯化、测序等,比较其序列差异。结果六种常见嗜尸性蝇类相互之间序列差异明显,同一种蝇的成虫、幼虫、蛹之间未见差异。结论mtDNACOI区序列分析可作为法医学嗜尸性蝇类种属鉴别的可靠方法。     

河南三门峡地区夏秋季常见嗜尸性蝇类的初步研究

目的探讨三门峡地区常见嗜尸性苍蝇种类、演替规律及其在法医学实践中的应用价值。方法采用笼诱法观察7月中旬-10月中旬兔尸上嗜尸性苍蝇种类演替规律及生活习性。结果出现的双翅目嗜尸性苍蝇有3科9属13种,主要为蝇科的舍蝇、市蝇、厩腐蝇、元厕蝇、斑蹠黑蝇、兰翠蝇;丽蝇科的大头金蝇、丝光绿蝇、亮绿蝇、巨尾阿丽蝇;麻蝇科的棕尾别麻蝇、褐须亚麻蝇和尾黑麻蝇;且出现时间有很强的规律性。结论河南三门峡地区夏秋季常见嗜尸性蝇类在兔尸上的出现有一定的演替规律,可望为该地区法医学死亡时间的推断提供参考。     

利用尸食性蚤蝇推断死亡时间的法医学研究进展

死亡时间的准确推断一直是法医学的难题。昆虫学方法已被认为是死亡时间推断的有效方法。尸食性蝇类发育生物学在死亡时间推断中有着重要地位。蚤蝇体形微小,在相对密闭的空间,可成为尸体上主要的甚至是唯一的昆虫证据。本文从尸食性蚤蝇的作用、种属鉴定以及日龄推断方面,综述了利用尸食性蚤蝇推断死亡时间的法医学研究进展。     

书讯

正《中国尸食性蝇类》一书由贵州警官职业学院陈禄仕教授主编,丛斌院士着序,国家出版基金资助,精装本,98元/本。该书共为4篇(14章节及附录),图文并茂,黑白图180幅,彩色图59幅,表格65个。第1篇记述蝇类的体位及名称,蝇类成虫基本特征,蝇类3龄幼虫基本特征,蝇类生活史及习性,蝇类与法医学的关系等;编制有尸食性蝇类成虫分科检索表,三龄幼虫分科检索表,蝇蛹检索表等。第2篇记述目前我国与尸体有关的尸食性蝇类9科、17亚科、49属、105种成虫和部分蝇卵、幼虫和蛹的基本形态特征,以及分布和生态学特征,附有属、种检索表。第3篇记述尸食性蝇类在犯罪调查中的作用,如推测死亡时间、死亡原因、尸源区域、尸体现场及致伤部位     

呼和浩特地区夏秋季常见嗜尸性蝇类的研究

目的研究呼和浩特地区常见嗜尸性苍蝇种类及其出现规律。方法观察法研究7～10月份兔尸上嗜尸性苍蝇种类变化。结果该地区兔尸上出现的双翅目嗜尸性苍蝇3科8属10种,主要有蝇科的家蝇、舍蝇、开普黑蝇、刺足齿股蝇、厩腐蝇;丽蝇科的丝光绿蝇、大头金蝇、铜绿蝇;麻蝇科的棕尾别麻蝇、肥须亚麻蝇。上述蝇类在尸体上出现时间及部位表现出很强的规律性。结论研究结果有望成为法医在呼和浩特地区对尸体进行死亡时间推断的依据。     

利用积温和昆虫发育历期推测死亡时间的研究

目的积累尸食性蝇类虫态发育历期和积温的资料。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6种尸食性蝇类的虫态发育历期和积温进行观察研究。结果经过观察,取得了棕尾别麻蝇、丝光绿蝇、紫绿蝇、宽丽蝇、巨尾阿丽蝇、大头金蝇等6种尸食性蝇类的虫态发育历期和积温的基础数据。并采用倒计积温的方法推测实际案例中死者死亡时间,破案后证实推测时间与实际死亡时间一致。结论本文数据可为利用尸食性蝇类虫态育历期的积温推测死亡时间提供依据。     

基于翅脉的图像数字化分析进行嗜尸性蝇类种类鉴定

目的基于翅脉的图像数字化分析对常见嗜尸性蝇类进行种类鉴定,为法医昆虫学中嗜尸性蝇类快速、准确的物种鉴定提供新的思路。方法用腐肉野外随机诱捕棕尾别麻蝇、绯角亚麻蝇、酱亚麻蝇、拟东方辛麻蝇、红尾粪麻蝇、巨尾阿丽蝇以及裸芒综蝇7种常见的嗜尸性蝇类雌雄成虫共226只,对每只苍蝇右翅的17个标志点进行数字化处理和图像分析,利用置换检验评估异速生长效应的影响,典型变量分析(canonical variate analysis,CVA)对7种嗜尸性蝇类物种间以及雌性物种间的翅形变化情况进行分析,交叉判别验证对分类的可靠性进行评价。结果在7种嗜尸性蝇类物种间和雌性成虫物种间,异速生长的影响具有统计学意义(P0.05)。CVA结果表明在7种嗜尸性蝇类物种间和雌性物种之间,翅膀形状变化具有明显的差异性,前2个典型变量占据了翅脉形状总变异的82.9%和84.1%。利用翅脉的图像数字化分析可以区分这7种常见的嗜尸性蝇类,总体种类判别准确率为81.2%～100.0%,7种雌性蝇类的种类判别准确率为75.0%～100.0%。结论基于翅脉的图像数字化分析是一种较为简便、可靠的昆虫物种鉴定的方法,可用于常见嗜尸性蝇类的种类鉴定。     

石河子春季常见尸食性昆虫种类及丝光绿蝇发育观察

目的观察新疆石河子市区尸食性昆虫的种类及温度对优势种丝光绿蝇生长发育的影响。方法 2007年和2008年的4月15日至6月15日在石河子市（E44.18°、N86.00°）3个不同地点诱集尸食性昆虫,并鉴定分类。将优势种丝光绿蝇在不同温度下饲养,观察其体长、体重、羽化率、雌雄比、历期等生长发育特点。结果石河子地区春季3个不同地点共诱集到尸食性昆虫6目14科16种,其中以膜翅目、双翅目和鞘翅目为主;丝光绿蝇幼虫体长、体重随着温度升高而增长、增加,化蛹时又有所缩短、减轻;不同的温度对幼虫的羽化率和雌雄比影响不明显。结论本文所得数据可为新疆石河子地区的法医昆虫学及相关研究和实践提供一定参考。     

Effect of different post-feeding intervals on the total time of development of the blowfly Lucilia sericata (Diptera: Calliphoridae)

By estimating the age of the immature stages of flies developing on a corpse, forensic entomologists are able to establish the minimum post-mortem interval. Blowflies, which are the first and most important colonizers, usually leave the cadaver at the end of the last larval stage searching for a pupation site. This period of development is referred as the post-feeding or wandering stage. The characteristics of the ground where the corpse was placed might be of notable importance for the post-feeding dispersal time: For pupariation the larvae prefer an environment protected from light and predators and may have a longer dispersal time in order to reach an appropriate pupation site. Hence, the dispersal time can vary and may influence the total time of development which may lead to an erroneous calculation of the post-mortem interval. This study investigates the effect of various post-feeding time intervals on the development of the blowfly Lucilia sericata at a temperature of 25°C. As larvae reached the post-feeding stage a pupariation substrate was offered at 0 and after 12, 24 and 48h. Only the larvae with a dispersal time of 24h (total time of development 325.2h; median) and 48h (total time of development 347.7h; median) showed a significantly longer total development time compared to the control group (total time of development 318.4h; median). The mortality rate did not differ between groups; however the flies that emerged from the group with a dispersal of 48h were significantly smaller indicating increased energy consumption during dispersal. The results of this study indicate that a prolonged post-feeding stage could increase the total developmental time of L. sericata which should be taken into consideration when interpreting entomological findings. The need for a serious examination of current rearing practices in forensic entomology laboratories is indicated because reference data sets for the time of development are usually produced by offering the post-feeding stage a substrate for pupariation immediately.     

Growth rates of the blowfly, Lucilia sericata, on different body tissues

Estimates of post-mortem interval based on forensic analysis of the age of blowfly larvae on a corpse, are generated from standardised larval development curves. These are derived from studies of the growth of larvae reared, usually, on liver and at a range of temperatures. However, it is possible that the species or organ on which the larvae feed, might significantly alter the rate of growth. The present study therefore compared the development of the blowfly Lucilia sericata (Meigen) (Diptera: Calliphoridae) fed on lung, liver and heart, from both cows and pigs. Half of the tissue samples used were liquidised while half were not, to assess whether structural differences in the food source were important. Larvae grew significantly faster and gave rise to larger adults when reared on pig compared to cow tissue and when reared on lung and heart compared to liver. Larvae completed feeding and wandered from the food source 31h earlier and grew 2mm longer when reared on lung compared to liver. Tissue structure had no or little effect on development. For the forensic entomologist, these results highlight the importance of recording the position of larvae removed from a body and the care that should be used when extrapolating development rates from standard curves based on larvae fed on only a single medium, particularly where that is liver.     

Influence of substrate tissue type on larval growth in Calliphora augur and Lucilia cuprina (Diptera: Calliphoridae)

The size of fly larvae is an important variable in the use of these insects to estimate postmortem interval. Furthermore, the nutritional intake of larvae is likely to vary subject to the part of a corpse on which they are feeding. A study was therefore conducted to investigate the effect of type of food substrate on larval growth in two species of forensically important Australian blowflies. After collection on sheep's liver in the laboratory, different groups of larvae of Lucilia cuprina (Wiedemann) and Calliphora augur (Fabricius) were grown on sheep's liver, meat, and brains, and their body lengths compared. Results indicated that the development of larvae fed sheep's liver was adversely affected compared with larvae fed meat and brain; they moulted later, reached maximum length more slowly and sometimes produced significantly smaller pupae. These findings, similar to those of another recent study, have obvious implications for postmortem interval determinations. Estimates may be considerably skewed if the site of collection of larvae at a death scene contains tissue types different to those used in reference experiments. We therefore recommend caution in forensic analyses that interpret crime scene data using developmental studies performed with a single type of larval food substrate.     

Seasonality of insect succession and pig carcass decomposition in a natural forest area in southeastern Brazil

In this study, successional patterns, relative abundance of larvae and adults of sarcosaprophagous insects, carcass decay, diversity and seasonality of species, and their potential as forensic indicators were studied. Four experiments were carried out in each season in a natural area of southeastern Brazil. Two pigs (Sus scrofa L.) were used in each experiment and were exposed to sunlight and shade, respectively. The Calliphoridae outnumbered the Sarcophagidae in specimens collected and reared from the carcasses. More insects were collected from carcasses exposed to the sun, while a larger number of specimens were reared from those in the shade. Temperature and rainfall influenced the stages of carcass decay and insect activity and abundance. Chrysomya albiceps was the most abundant species in all four experiments. The carcasses were used as a protein source and substratum for oviposition. The dark putrefaction and fermentation stages yielded more flies than the other stages. These results show that flies are important in carcass decay and are, therefore, also of forensic importance. Seven species can be considered valuable forensic indicators in Southeastern Brazil. However, only three species were useful as forensic indicators in wooded areas: P. intermutans, H. segmentaria, and H. semidiaphana.     

北京地区法医昆虫学研究──Ⅱ.尸体分解过程中的昆虫种类演替与死亡时间推断

在调查北京地区嗜尸性昆虫物种谱系的基础上，进一步研究了在尸体分解过程中，昆虫种类的演替特点及其对死亡时间推断的价值。嗜尸性昆虫侵食尸体的过程可分为侵入期、分解期和残余期：侵入期以双翅目蝇类为主，时间推断以幼蛆的发育程度为依据；分解期出现大量鞘翅目种类，时间推断以甲虫的各类组成、数量以及演替特征为主要依据；残余期昆虫数量极少。季节及温度、环境条件、尸体是否受伤或裸露，是影响昆虫侵食尸体时序的三个重要因素。正常的春季，侵入期为8至25天，分解期为约42天。     

Forensic genetic analysis of insect gut contents

Entomological evidence is most often used for estimating the postmortem interval, but fly larvae can also be a source of vertebrate DNA. Forensic analysis of DNA recovered from a larva's gut can be used to identify what the larva had been feeding on. During our previous research studies, we used the same DNA extraction for the dual purpose of identifying the insect species and associating a maggot with its last meal. In our experience, we have encountered several situations where this method for associating a maggot with a corpse would have been useful, such as removal of remains from a suspected crime scene, an alternative food source is nearby the scene or the body, and a chain-of-evidence dispute. However, since maggot gut content analysis is a quite brand-new area of study, many of the limitations of the technique have not yet been explored. The results of our most recent research studies suggest that third-instar larvae actively feeding on the corpse can be considered the best source of human DNA, better than postfeeding or starved larvae. In this paper, the state of the art of forensic genetic analysis of maggot gut contents is reviewed.     

Growth behavior of the blue blowfly Calliphora vicina maggots

Fifty-three clusters of blowfly eggs of the genus Calliphora vicina were observed in the laboratory up to the hatching stage under reproducible and virtually field-like conditions. Rearing the larvae was then continued up to pupation, the larval growth in length being recorded several times a day. As the object was to study the dependence of the larvae increase in length on the temperature conditions in vitro, the substratal humidity and food supply were kept unchanged during the entire study. The temperature ranged from 6.5 degrees C to 35 degrees C, with the temperature for the individual cluster kept constant during the entire developmental process. Data on about 5500 measured larvae were statistically evaluated. The basic result established was that in the case of the blowfly of the genus Calliphora vicina in vivo, all developmental stages relevant to the entomologic determination of the time of death depend on the temperature conditions: (1) the duration of the egg stage increases with decreasing temperature; (2) the speed of larval growth is slower at lower temperatures; (3) the maximal larval length is reached earlier at higher temperatures; (4) the mean value of maximal length decreases with increasing temperature; (5) larvae under all temperature conditions decrease in size after having reached their maximal length, the decrease in length being more rapid at higher temperatures; (6) constant temperatures over 30 degrees C lead to "stunted forms" which do not pupate and die; (7) constant temperatures under approximately 16 degrees C after the peak of growth has been reached inhibit the readiness to pupate, which causes the larvae to fall into a stationary state of rest, which will be interrupted only when the temperature is raised and resumption of the metamorphosis is thus induced. To allow rapid reconstruction of the larval age in general practice, the established growth data were set out in the form of a diagram designated isomegalendiagram, which permits temperature-fluctuation-related entomologic determination of the time of death with a maximum degree of accuracy.