Insect succession and carrion decomposition in selected forests of Central Europe. Part 1: Pattern and rate of decomposition

Pig carrion decomposition and insect succession were monitored in different seasons and forests of Central Europe. Pattern of decomposition as well as onset, duration and rate of decompositional processes were measured. Pattern of decomposition was the same in almost all cases with putrefaction, active and advanced decay. In the majority of carcasses active decay was driven by larvae of Calliphoridae with a clear seasonal shift in dominant taxa. However, in some spring, alder forest cases active decay was driven by larvae of Necrodes littoralis (Coleoptera: Silphidae). As a rule the mosaic decomposition was observed. In spring a significant delay in onset of all decompositional processes was found. Season significantly affected rate of active decay due to a much higher rate in summer. Decomposition in alder forest proceeded faster than in pine-oak forest and hornbeam-oak forest. Differences between the latter two forests were practically negligible. Implications for forensic entomology are discussed.     

Variation in decomposition stages and carrion insect succession in a dry tropical climate and its effect on estimating postmortem interval

Insects have an important role in minimum postmortem interval (PMI_min) estimation. An accurate PMI_min estimation relies on a comprehensive study of the development and succession of local carrion insects. No published research on carrion insect succession exists for tropical north Queensland. To address this, we aimed to obtain preliminary observational data concerning the rate of decomposition and insect succession on pig carcasses in Townsville and compare these with other regions of Australia and overseas. Adult insects were collected daily from three pig carcasses for 30 d during summer and identified to family level. Observations of decomposition rate were made each day and progression through the stages of decomposition were recorded. Adult insects were identified to family and their presence/absence used as a proxy for arrival at/departure from the remains, respectively. These preliminary data highlight several interesting trends that may be informative for forensic PMI_min estimation. Decomposition was rapid: all carcasses were at the dry/remains stage by Day 5, which was substantially quicker than all other regions in the comparison. Differences were also observed in the presence/absence of insect families and their arrival and departure times. Given the rapid progression through early decomposition, we argue that later-arriving coleopteran taxa may be more forensically informative in tropical Australia, in contrast with temperate regions where Diptera appear most useful. This research contributes preliminary observational data to understanding insect succession patterns in tropical Australia and demonstrates the critical need for comprehensive local succession data for each climatic region of Australia to enable accurate PMI_min estimation. These data will inform future research targeted at gaining a more comprehensive understanding of insect succession in the Australian tropics.

Key points:

• We obtained preliminary observational data concerning the rate of decomposition and insect succession on pig carcasses in tropical Australia.
• Decomposition was rapid: all carcasses were at the dry/remains stage by Day 5.
• Coleopteran taxa may be more forensically informative in tropical Australia than dipterans.

     

Insect succession and decomposition patterns on shaded and sunlit carrion in Saskatchewan in three different seasons

A study was conducted on decomposition and insect succession in the Prairie Ecozone of Saskatchewan in the year 2000. Eighteen domestic pig carcasses (42-79 kg) were employed as human models for applications to future homicide investigations in this region. Two major variables were considered including the effect of season and habitat (sun versus shade). Research was conducted over 25 weeks, spanning three seasons: spring, summer and fall. Ambient temperature, internal carcass temperature, faunistic succession over time, and the rate of decay were all compared for each experimental variable. Results indicated that habitat was only a factor in the decompositional rate of carrion in the spring season. The ambient temperature was the chief factor determining the seasonal variations in decay rate. Maximum internal carcass temperatures always coincided with the presence of 3rd instar larvae. Patterns of insect succession occurred in a predictable sequence that varied across different habitats and seasons and was unique compared to previously published studies. Carcasses placed in spring and fall attracted a more diverse assemblage of insects than summer-placed carrion. Sun-exposed carrion also had greater variation in fauna than shaded carrion in spring and fall. Members of Silphidae were the first coleopteran colonizers in all habitats and seasons. This paper also marks the first record for Cochliomyia macellaria (Fabricius) in Saskatchewan.     

An initial study of insect succession and carrion decomposition in various forest habitats of Central Europe

At the end of summer and beginning of fall 2005 insect succession and pig carrion decomposition were studied in pine-oak forest, hornbeam-oak forest, and alder forest in Western Poland (Central Europe). Five stages of decomposition were recognized: fresh stage, bloated stage, active decay stage, advanced decay stage, and remains stage. The highest rate of decomposition was observed in the alder forest and the lowest in the pine-oak forest. A similar composition of carrion entomofauna was found in each forest. Numerous adults of Lucilia caesar, Phormia regina and Calliphora vomitoria (Calliphoridae), Hydrotaea spp. (Muscidae), Stearibia nigriceps and Parapiophila vulgaris (Piophilidae), Necrodes littoralis and Thanatophilus rugosus (Silphidae), Creophilus maxillosus, Omalium rivulare, Oxypoda acuminata and Philonthus spp. (Staphylinidae) as well as larvae of L. caesar, P. regina, C. vomitoria, Fannidae (Diptera) and N. littoralis, C. maxillosus, Philonthus (Coleoptera) were collected. There were no differences between forests in the sequence of insect occurrence on carrion. However, differences between forests in occurrence time and activity period of some taxa were found. Implications of these results for forensic entomology are discussed.     

Yearly activity patterns in southern Victoria (Australia) of seasonally active carrion insects

Some seasonally active carrion invertebrates leave remnants of their presence that remain long after the completion of flesh decay. Remnants may include fly puparia (pupal cases) or insect exoskeletal elements. The presence of these remnants among old, decomposed remains can therefore indicate possible months in which death occurred. A large-scale study of the patterns of neonatal piglet decomposition and carrion insect succession in a forest was carried out in 1999 and 2000. Five fresh piglet carcasses were exposed once per season in both years and visited frequently throughout decay. Ten seasonally active taxa, likely to leave durable remnants of their presence were selected, and profiles were constructed of their activity times over the 2-year study.     

The succession and development of insects on pig carcasses and their significances in estimating PMI in south China

The succession of insect communities on carrion varies at local and global spatial scales. As such, ecological succession data obtained from corpses at one geographic location cannot necessarily be applied to other locations. Our study describes this succession in the far southern part of China to provide such data for forensic cases in this region. A total of 18 pig carcasses were placed in the field in four seasons, and the timing of the following events were recorded: appearance of larvae, onset of larval wandering, when most larvae had wandered, onset of pupariation, when most larvae had pupariated, onset of eclosion and end of eclosion. Our results indicated that all of the evaluated events could be used as accurate indicators of postmortem interval (PMI). The carcasses decayed fairly quickly in spring, summer and autumn, taking 225+/-75 h, 183+/-44 h, and 247+/-70 h, respectively, to decay from the fresh stage to skeletonisation. In winter, carcasses needed longer (1180+/-291) to decay as much. Carcasses attracted 47 species of insect, with flies predominating. The larvae were mainly Chrysomya megacephala (Fabricius), Chrysomya rufifacies (Macquart) and Hydrotaea (Ophyra) spinigera (Stein). Most necrophagous insects were found all year around, and there were no marked differences in species among the four seasons, except that Dermestes maculatus (De Geer) was absent in winter. Blowflies produced only one generation on a carcass before it became skeletonised, which simplified the estimation of PMIs.     

Estimating the preappearance interval from temperature in Creophilus maxillosus L. (Coleoptera: Staphylinidae)

Abstract: Some carrion insects appear on carcasses late in decomposition. While using these late‐arriving taxa to estimate postmortem interval, it is vital to accurately estimate an interval preceding their appearance on a cadaver called the preappearance interval (PAI). This paper tests the possibilities of a PAI estimation from temperature in case of late‐arriving, predatory carrion beetle Creophilus maxillosus. The relationship between temperature and PAI of adult and larval C. maxillosus was modeled using the results of a large‐scale experiment on succession in forests of Central Europe. In both stages, PAI was found to be strongly, inversely related to temperature averaged for the duration of PAI. The PAI estimation from mean degree‐day accumulations (mDDA), estimated DDA, and “PAI*T” functions were tested using external successional data. The greatest accuracy of PAI estimates was achieved using an exponential “PAI*T” function.     

Estimating the pre-appearance interval from temperature in Necrodes littoralis L. (Coleoptera: Silphidae)

While estimating post-mortem interval from entomological evidence it is useful to divide it into two separate intervals: the pre-appearance interval (PAI) and the development interval in the case of immature insects and PAI and the presence interval in the case of adult insects. An accurate estimate of PAI is critically important particularly in the case of those insects which appear on remains late in decomposition. In this paper the possibilities of PAI estimation from temperature are evaluated in late-arriving, forensically important carrion beetle Necrodes littoralis. The relationship between PAI of adult and larval N. littoralis and temperature was modelled by using results of succession experiments in forests of Central Europe. In both stages PAI was found to be strongly, inversely dependent on mean daily ground level temperatures averaged for the duration of PAI. Several methods of PAI estimation were proposed and their accuracy was initially evaluated with external successional data.     

Diversity of Forensic Rove Beetles (Coleoptera,Staphylinidae) Associated with Decaying Pig Carcass in a Forest Biotope

Most forensic studies are focused on Diptera pattern colonization while neglecting Coleoptera succession. So far, little information is available on the postmortem colonization by beetles and the decomposition process they initiate under temperate biogeoclimatic countries. These beetles have, however, been referred to as being part of the entomofaunal colonization of a dead body. Forensic entomologists need increased databases detailing the distribution, ecology, and phenology of necrophagous insects, including staphylinids (Coleoptera, Staphylinidae). While pig carcasses are commonly used in forensic entomology studies to surrogate human decomposition and to investigate the entomofaunal succession, very few works have been conducted in Europe on large carcasses. Our work reports the monitoring of the presence of adult rove beetles (Coleoptera, Staphylinidae) on decaying pig carcasses in a forest biotope during four seasons (spring, summer, fall, and winter). A total of 23 genera comprising 60 species of rove beetles were collected from pig carcasses.     

Insect fauna visiting carrion in Southwest Virginia

Successional patterns of insect fauna on pig carcasses were studied in southwest Virginia. The objective was to identify and qualitatively assess the major taxa of forensic importance in this region. Studies were conducted in spring and summer 2001 and 2002, and fall 2002. Over 50 taxa were collected and identified. Phormia regina was the dominant fly species in the spring (>90%) and co-dominant with Phaenicia coeruleiviridis in the summer. Phaenicia sericata, Lucilia illustris, and Calliphora spp. were collected in spring and summer, but less frequently. Eleven species of Sarcophagidae also were collected with Sarcophaga utilis and Helicobia rapax the most common. In the fall, the dominant fly species were Calliphora vomitoria, L. illustris, and P. coeruleiviridis. The primary beetle species collected in spring and summer included three Staphylinidae (Creophilis maxillosus, Platydracus maculosus, and Aleochara lata) and three Silphidae (Oiceoptoma noveboracense, Necrodes surinamensis, and Necrophila americana). No beetles were collected in the fall.     

Decomposition and insect succession of clothed and unclothed carcasses in Western Australia

The effect of clothing on carcass decomposition and patterns of insect succession onto remains were investigated in two separate years during autumn in Western Australia. The progression of decomposition differed between clothed and unclothed carcasses in both years of the study. The presence of clothing markedly prolonged the wet decay stage in both years with larval feeding occurring across the moist skin surface underneath clothing, as well as within and under the carcasses. Ambient temperatures were higher in the second year of the study and corresponded to marginally faster rates of decay throughout decomposition. Within years, insect arrival and oviposition were largely consistent between clothed and unclothed carcasses with a few notable exceptions. The green blow fly, Lucilia sericata Meigen (Diptera: Calliphoridae) oviposited one day earlier on clothed than unclothed carcasses in both years of the study. The black carrion fly, Australophyra rostrata Robineau-Desvoidy, (Diptera: Muscidae) colonised clothed carcasses in two distinct waves of succession but only one wave of ovipoistion was observed on unclothed carcasses in either year. Correspondingly, clothed carcasses supported larval feeding by A. rostrata for a longer duration than unclothed carcasses. Finally, dipteran larval masses were more widely distributed across the carcass surface and were present for a longer period of time on clothed carcasses than on unclothed carcasses in both years. Forensically relevant data detailing the seasonal pattern of insect succession onto clothed and unclothed decomposing remains in Western Australia are reported.     

Piophila megastigmata (Diptera: Piophilidae): first records on human corpses

Piophila megastigmata McAlpine, 1978, for many years only known from South Africa, was recently recorded in Spain. The present work reports for the first time the occurrence of P. megastigmata in human corpses in Portugal. The species was also collected in succession studies conducted with piglet carcasses, where it coexisted with Stearibia nigriceps (Meigen, 1826), showing similar periods of presence in the carcass. However, P. megastigmata was more abundant than S. nigriceps in autumn, with the opposite in summer. During winter neither species was able to colonize carrion and in spring, only S. nigriceps. This first record of P. megastigmata in human corpses confirms it as a potentially useful forensic species in Europe. The species, well established in the Iberian Peninsula, probably has a wider distribution but has been previously overlooked and possibly confused with Piophila casei (Linnaeus, 1758) in many studies.     

A preliminary survey of carrion breeding insects associated with the Eid ul Azha festival in remote Pakistan

In Pakistan, the three days of Islamic festival of Eid ul Azha (Eid) are characterized by millions of livestock sacrifices and availability of countless breeding resources for insects of forensic importance. Thus during Eid, December, 2008, in a Pakistani village observing 70 sacrifices, we examined postmortem insect attractions on various sacrificial products (from 23 animals), i.e., blood pools, meat, hides/skins, bones, offal and real time insect succession on goats' offal at five dump sites. Thirty five insect species were collected from 14 indoor and outdoor sites. Offal at the dump sites attracted most insect species both by taxa and in numbers, followed by hides in the court yards, meat (40-70 kg/animal) in kitchens and blood pools in the court yards. Synanthropic calliphorids and muscids were found to be exclusive indoor "first and only arrivals" in comparison to a diverse array of first day insect arrivals at dump sites including calliphorids, sarcophagids, muscids, sphaerocerids, sepsids, empidids, gryllids and formicids. Though burial is usually considered as a barricade between most insect species and carrion yet dump site A with an early burial but also earliest insect colonization showed the fastest rate of decomposition. No vertebrate scavenging at any of the offal dump sites perhaps showed their private feeding inclination, thus implying that in times of mass slaughters most of the dumped winter carrion products in human vicinities are either consumed by insects and/or are buried. Here we also suggest a high rate of fly dispersal during Eid which if true has consequences for forensic investigations in Muslim populace areas especially during the Eid.     

Portion size matters: Carrion ecology lessons for medicolegal death investigations—A study in Cape Town,South Africa

Forensic taphonomic studies are regionally specific and improve time since death estimates for medico-legal casework. Within forensic taphonomy and carrion ecology, vertebrate scavengers are under-researched with many studies conducted using multiple, unclothed carcasses. This is a forensically unrealistic experimental design choice with unknown impact. The effect of variation in carrion biomass on the decomposition ecosystem, particularly where vertebrate scavengers are concerned, requires clarification. To assess the effect of carrion biomass load on vertebrate scavenging and decomposition rate, seasonal baseline data for single, clothed ~60 kg porcine carcasses were compared to clothed multiple-carcass deployments, in a forensically relevant habitat of Cape Town, South Africa. Decomposition was tracked via weight loss and bloat progression and scavenging activity via motion-activated cameras. The single carcasses decayed more quickly, particularly during the cooler, wetter winter, strongly correlated with concentrated Cape gray mongoose (Galerella pulverulenta) scavenging activity. On average and across seasons, the single carcasses lost 68% of their mass by day 32 (567 accumulated degree days [ADD]), compared to 80 days (1477 ADD) for multi-carcass deployments. The single carcasses experienced substantially more scavenging activity, with longer visits by single and multiple mongooses, totaling 53 h on average compared to 20 h for the multi-carcass deployments. These differences in scavenging activity and decay rate demonstrate the impact of carrion biomass load on decomposition for forensic taphonomy research. These findings need corroboration. However, forensic realism requires consideration in taphonomic study design. Longitudinally examining many single carcasses may produce more forensically accurate, locally appropriate, and usable results.     

Seasonal patterns of arthropods occurring on sheltered and unsheltered pig carcasses in Buenos Aires Province (Argentina)

Differences in the succession of insects and other Arthropoda (invertebrate animals with jointed legs), on domestic pig carcasses placed under a roof and under the open sky have been studied in Buenos Aires Province, Argentina (latitude 34 degrees 45'S) in all the seasons of the year. Faunal associations proved different for each treatment in winter: the common bluebottle Calliphora vicina was found in both, but on the sheltered carcass Cochliomyia macellaria and the rare Phaenicia cluvia were found as well. In the fall, the difference between sheltered and unsheltered carcasses was small (six species on the former and five species on the latter); in spring and summer, the difference was negligible.     

深圳地区夏季室内外猪尸体上嗜尸性昆虫的群落演替

目的：根据深圳地区夏季室内外猪尸体上主要嗜尸性昆虫的生长发育和群落演替规律来推断死亡时间（PMI）。方法从2013年5月初到8月初,在深圳市公安局法医检验中心模拟的室内、外场地分别放置成年猪尸体两头,观察尸体腐败的过程和猪尸体上出现主要昆虫的种类,记录猪尸体腐败各阶段的历期,以及主要昆虫在尸体上的群落演替。结果室内、外的猪尸体分别经历了412.5 h和325 h进入白骨化阶段。主要的嗜尸性昆虫,蝇类以大头金蝇、绯颜裸金蝇、星岛金蝇,甲虫类以大隐翅甲、赤颈郭公甲、丽腐阎甲、白腹皮蠹为优势代表性种类。室外猪尸体在较多雨水的影响下,优势蝇群明显产生二代,室内的猪尸体上未见较大规模二代产生。结论深圳地区夏季室内外猪尸体上主要昆虫的群落演替有规律性,7种代表性昆虫及其幼虫整体的活动规律对推断PMI有较大的意义。     

呼和浩特夏秋季嗜尸性苍蝇群落组成与演替

目的研究呼和浩特夏秋季常见嗜尸性苍蝇生态群落组成与演替规律。方法连续3年用观察法研究7—10月份,家兔、狗尸体、鸡、鱼内脏等试验材料上的嗜尸性苍蝇生态群落组成与演替。结果该地区上述尸体上出现的双翅目嗜尸性苍蝇是最先到达尸体上的昆虫,而且在尸体上出现时间及部位表现出很强的生态群落演替规律性。结论研究结果可成为在呼和浩特地区对尸体进行死亡时间、死亡地点推断的依据。     

Insect faunal succession on decaying rabbit carcasses in Punjab, India

Insect faunal succession on decaying rabbit carcasses was carried out at Punjabi University, Patiala (Punjab), India, from March 1997 to December 1999. Four stages of decomposition were recognized, i.e., fresh, bloated, decay, and dry. A total of 38 insect species belonging to four orders and 13 families were recorded. Diptera, Coleoptera, and Hymenoptera dominated the carrion fauna. Calliphorids were the first to arrive in all the seasons of the year. Five species of Calliphoridae, four of Sarcophagidae, ten of Muscidae, and one each from Anthomyiidae and Otitidae were observed on rabbit carcasses. Representatives of six Coleopteran families, i.e., Staphylinidae, Histeridae, Cleridae, Dermestidae, Tenebrionidae, and Silphidae, were recorded. Eight species belonging to family Formicidae (Hymenoptera) were also collected during the present studies. Only one species of Lepidoptera was observed on carrion.     

Associational Patterns of Scavenger Beetles to Decomposition Stages

Beetles associated with carrion play an important role in recycling organic matter in an ecosystem. Four experiments on decomposition, one per season, were conducted in a semirural area in Bahía Blanca, Argentina. Melyridae are reported for the first time of forensic interest. Apart from adults and larvae of Scarabaeidae, thirteen species and two genera of other coleopteran families are new forensic records in Argentina. Diversity, abundance, and species composition of beetles showed differences between stages and seasons. Our results differed from other studies conducted in temperate regions. Four guilds and succession patterns were established in relation to decomposition stages and seasons. Dermestidae (necrophages) predominated in winter during the decomposition process; Staphylinidae (necrophiles) in Fresh and Bloat stages during spring, summer, and autumn; and Histeridae (necrophiles) and Cleridae (omnivores) in the following stages during those seasons. Finally, coleopteran activity, diversity and abundance, and decomposition rate change with biogeoclimatic characteristics, which is of significance in forensics.     

A statistical analysis of successional patterns in carrion-arthropod assemblages: implications for forensic entomology and determination of the postmortem interval.

A set of statistical protocols is proposed for analyzing carrion-arthropod succession in forensic entomology investigations. A total of 23 carrion-arthropod data sets from temperate, tropical, desert, and coastal environments were assembled in a standard format and analyzed using randomization tests and methods derived from quantitative community ecology. The data were analyzed in three ways. First, patterns of arthropod visitation on nonhuman carcasses were analyzed in each of the 23 cases. Analysis revealed two groups of taxa: those that persist on the carcass over a single time interval (= nonreoccurring taxa, 80% of the taxa) and those that appear, leave, and reappear over time on the carcass (= reoccurring taxa, 20%). Reoccurring taxa, which can confound estimation of the postmortem interval (PMI), were found in 6 classes, 12 orders, and 29 taxonomic families of arthropods, including some forensically important taxa (for example, calliphorids, sarcophagids, histerids). The recognition that reoccurring taxa exist and that they are found in forensically important groups is an early step toward factoring in their potential importance in future entomological investigations. Second, temporal changes in the taxonomic composition of the carrion-arthropod community were studied by quantifying the degree of taxonomic similarity between pairwise combinations of time-specific samples of the succession. In 13 of the 18 illustrated cases, the midsuccessional samples, owing to their higher species richness, were taxonomically more similar to all other pairwise samples, on the average, than early and late successional samples which were poorer in species. Variability in taxonomic composition is the norm for most periods of the succession; however, in 17 of the 23 cases, some successional periods (particularly endpoint samples) revealed no changes in arthropod species composition (= matching sample-pairs). When applied to medicolegal cases, it is suggested that data sets with large fractions of matching sample-pairs should produce wider-ranging PMI estimates, on the average, than data sets with smaller fractions of matching sample-pairs. Third, Monte Carlo simulation was applied to each of the 23 assemblages to test specific hypotheses about community-wide patterns of arthropod visitation times on nonhuman carcasses. Simulation results revealed that arthropod residence times in the majority of cases (13 or 56%) followed a "clumped" succession model, whereas, the remaining 10 cases (44%) showed a more "uniform" spacing pattern of residence times on carcasses. Comparison of species accumulation curves for observed and simulated data further revealed that among the 13 "clumped" cases, most (9 or 69%) followed a "clumped, early" model (rather than "clumped, midterm" or "clumped, late" models).(ABSTRACT TRUNCATED AT 400 WORDS)