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

Forensic entomology in homicide cases: study of a corpse found inside a buried vehicle

Forensic entomology plays a crucial role in death investigations, particularly in estimating the postmortem interval (PMI). This study presents a forensic entomology case involving a corpse found in a buried utility vehicle. The victim was in an advanced state of decomposition, with autopsy findings revealing gunshot wounds. Cadaveric fauna was collected at the scene and during the autopsy. The analysis revealed a diverse insect community, with predominance of Compsomyiops fulvicrura and Piophila casei. The time of development of species like Dermestes maculatus and Necrobia rufipes was used to estimate the minimum PMI. The presence and low abundance of Calliphora vicina, a species preferring lower temperatures, shed light on the seasonal conditions at the time of death and suggested possible body concealment shortly after death. This research is the first to report insects as evidence in a corpse found in a buried vehicle and contributes to the body of knowledge in forensic entomology. The study also suggests that the use of entomological evidence can provide additional information about the season in which the body was concealed, making it a valuable tool in death investigation and crime scene reconstruction. Finally, it emphasizes the need for proper sampling, expert identification, and close collaboration between forensic entomologists and pathologists.

Origins and Diversification of Myiasis Across Blowflies

Parasitism represents a prevalent and successful ecological strategy that has evolved independently numerous times across metazoa. Understanding the origin and diversification of parasitism is a central question in evolutionary biology. This study investigated the evolutionary path leading to a specific form of parasitism in blowflies known as myiasis, where larvae develop on or within a vertebrate. We modeled myiasis-associated traits, including trophic specialization (obligatory parasitism, facultative parasitism and saprophagy), larval food substrate (necrotic, fresh or both) and developmental temperature (constant, variable or both) across the blowfly phylogeny. Our results suggested that the ancestral state of blowflies likely encompassed saprophagy or facultative parasitism, with larvae developing in corpses or necrotic tissues from wounds in either homeothermic or heterothermic hosts. Furthermore, our analysis highlights the role of facultative parasitism as an intermediate step for obligate parasitism in blowflies, indicating that pre-adaptations for a facultative parasitic lifestyle may serve as stepping stones for emerging obligate parasitism. These findings shed light on the complex evolutionary history of blowfly vertebrate parasitism, emphasizing the importance of facultative parasitism as a critical transitional stage in this evolutionary process.

Research Status of Sarcosaprophagous Beetles as Forensic Indicators

In forensic entomology, research focused on sarcosaprophagous flies, but the sarcosaprophagous beetles, as important "forensic indicator species" of late-stage PMI in cadaver decomposition, received less attention. To increase attention on, and use and understanding of, sarcosaprophagous beetles in forensic entomology, this paper presents a bibliometric analysis of the available relevant literature. The occurrence frequency of beetle families and species from succession studies, actual cases, and experiments were calculated and illustrated using graphs. As a result, a total of 14 families and 1077 species associated with carcasses were collected, with Staphylinidae being the most frequently recorded among the families, and Necrobia rufipes (Fabricius, 1781) (Coleoptera: Cleridae) being the most frequently recorded species. In addition, a brief introduction of the cadaver-related beetles of each family is given, and research on the species identification of the immature stages, age estimation of the immature stages, and estimation of the arrival time of sarcosaprophagous beetles are discussed and prospected. This work will aid in the increased use of sarcosaprophagous beetles in forensic science practice in the future.

Seasonal diversity and dynamics of entomofauna associated with the decomposition of pig (Sus scrofa domesticus L.) carcasses in a Peri-urban area of Central Burkina Faso, West Africa

This study aimed to determine the effects of seasons on the diversity and dynamics of insects associated with pig carrion in Gampela, Plateau Central Region, Burkina Faso, West Africa. Pig carcasses (Sus scrofa domesticus L.) were exposed in an open area to monitor their decomposition process and their colonization by insects during a warm and dry period (March-April 2015), a warm and wet period (August-September 2015) and a cool and dry period (December 2015-January 2016). Monitoring and entomological data collection occurred for 60 days for each study period. The decomposition process always included five stages (fresh, bloating, putrefaction, postputrefaction, and skeletal), which varied in duration depending on the study period. In sum, 118,761 insects belonging to 4 orders, 12 families, 17 genera, and 21 species were collected during the three study periods, with approximately 61% of the individuals collected during the warm and wet period. The dynamics of insect populations associated with the pig carcasses included two peaks at each study period. Formicidae was the most abundant insect family in each study period, but Musca domestica was the most abundant species. The listed species were found to belong to four trophic groups with a predominance of predators/carnivores followed by necrophagous insects. The orders, families, and trophic groups reported in this study were significantly more abundant during the warm and wet period. The results show prospects for the use of Calliphoridae, Muscidae, and Dermestidae in criminal investigations, depending on seasonal variations in Sudano-Sahelian areas.

Direct relationship between evapotranspiration rate (ETO) and vertebrate decomposition rate

When vertebrate scavenging is excluded, the Evapotranspiration Rate (ETo) of a given geographic region directly regulates the decomposition rate of unclothed vertebrate carrion, with any deviation attributed to insect activity. We conducted four decomposition experiments using pig carrion (Sus scrofa domesticus) over the span of two years (2018-2020) at a location in Davis, California. We used ETo, a variable that accounts for five climatic parameters (wind, temperature, humidity, solar radiation, and altitude) as the rate-determining variable of the decomposition process. We found ETo to have a strong (R2 = 0.98) predictive relationship with the decomposition rate. To account for maggot activity decomposing the carrion, we measured maggot weight in 2019 and 2020 using a novel method, and in 2020 we used FLIR imagery to measure maggot mass temperatures as a surrogate measurement of total maggot activity. Maggot activity was a significant predictor (p < 0.0001) of the decomposition rate, while maggot weight was not (p > 0.1). We hope to show the forensic entomology community the potential of using ETo. Future projects can incorporate ETo as a baseline to decomposition studies to determine if ETo remains the most accurate descriptor of decomposition and ultimately increase certainty in the Postmortem Interval (PMI).

A global perspective of forensic entomology case reports from 1935 to 2022

Forensic entomology case reports are the product of rapid development in the field, the widespread acceptance of the science and the application of forensic entomological knowledge. In this study, we retrospectively summarized information derived from 307 forensic entomology case reports from 1935 to 2022 from a global perspective. Our checklist of relevant information included insect species, specific indoor or outdoor preferences, preferred temperatures, and stages of body decomposition. Finally, a concept and calculation method for postmortem interval (PMI) estimation accuracy was proposed. There were 232 cases using insect developmental data and 28 cases using succession patterns to estimate PMI. A total of 146 species of insects were involved in the cases, of which 62.3% were Diptera and 37.7% were Coleoptera. Postmortem intervals were estimated from eggs in 4 cases, larvae in 180 cases, pupae in 45 cases, and puparia in 38 cases. The majority of cases were from June to October, and the average number of species mentioned in the cases was more at 15-30 °C. Considering the standardization of application, in the majority of cases, insect evidence was collected by other personnel and sent to forensic entomologists, there was a delay in the sampling, and the scene or meteorological data were directly used without correcting. Our data shows that there are still many shortcomings in the universality and standardization of forensic entomology in its practical application.

Interactive Key for Third Instar Larvae of Neotropical Blow Flies (Insecta, Diptera, Calliphoridae): the Contribution of Computational Tools to Assist in Species Identification

Calliphoridae (Insecta, Diptera), popularly known as blow flies or carrion flies, as most are necrophagous comprises one of the most relevant families of insects on forensics. Currently, more than 1500 blow fly species are known, the majority of which can be found in the Old World. In the Neotropics, it is estimated that there are approximately 20 species of forensic importance. In view of the taxonomic impediment associated with the identification of immatures, in this study, we present an interactive identification key for third instar larvae of necrophagous Calliphoridae species. This key includes 12 Neotropical blow fly species of forensic importance, more than 70 pictures, schemes, and definitions glossary and is free to access.

A Preliminary Study of Body Decomposition and Arthropod Succession in an Arid Area in Northwest China During Summer

The study of insect fauna and their development and succession patterns on decaying cadavers is crucial to promoting insect evidence as a useful tool in forensic science, particularly for estimating the postmortem interval (PMI). Body decomposition and arthropod succession are affected by many factors and exhibit substantial regional variations; therefore, detailed succession studies in different biogeographic regions are required for understanding the successional patterns of insects in various environments. This study was conducted in the summer of 2021 using three domestic pig carcasses (Sus scrofa domestica L., 1758) in the field of Shizuishan City, Ningxia, Northwest China. A total of 40 species of necrophagous insects belonging to three orders and 16 families were collected. Among Diptera, Lucilia sericata (Meigen,1826), Chrysomya megacephala (Fabricius,1794), and Phormia regina (Meigen,1826) (Diptera: Calliphoridae) were the dominant species. As for Coleoptera, the dominant species changed throughout the process of carcass decomposition from Saprinus semipunctatus (Fabricius,1792) (Coleoptera: Histeridae) to Dermestes maculatus DeGeer,1774 and Dermestes frischii Kugelann,1792 (Coleoptera: Dermestidae). The carcasses desiccated rapidly and reached the remains stage under extreme conditions of high temperatures and low humidity, after which a large amount of dried tissue of the carcasses attracted populations of Coleoptera, particularly Dermstidae, which were abundant and remained until the end of the experiment on day 50. The current study is the first forensic entomological investigation of succession in Northwest China and provides basic data for the estimation of PMI during summer in this region.

Sarcosaprophagous Muscid Fly (Diptera: Muscidae) Assemblages Along an Anthropized Gradient in the Humid Chaco Ecoregion, Chaco Province, Argentina

Deforestation, agriculture, farmyard animal husbandry, and urbanization are known to be the main causes of biodiversity loss and habitat fragmentation. The present study evaluated the role of anthropization in modulating Muscidae (Diptera) assemblages in the Humid Chaco ecoregion of Argentina, by testing the biotic homogenization and intermediate disturbance hypotheses. The study focused on natural, rural, and urban habitats in San Lorenzo Department, Chaco Province, where sarcosaprophagous muscid flies were surveyed. A total of 1,343 muscid flies were captured and identified to 7 genera and 24 species and morphospecies. We observed the effect of anthropization on the structuring of the assemblages and the presence of exotic species associated with human activity resulting from biotic homogenization. The highest abundance was recorded in the urban habitat, while the highest species richness and diversity (Shannon-Wienner and Hill's numbers) were found in the rural habitat, supporting the intermediate disturbance hypothesis. Several species are classified as indicators of habitat as well as according to their index of synanthropy. Our results provide valuable information about the use of sarcosaprophagous muscids as indicators of disturbance of natural habitats and about possible health risks related to this family of Calyptratae flies previously unsurveyed in northeastern Argentina. This information could be used in the ecological, agronomy, sanitary, and forensic fields.

Factors influencing carrion communities are only partially consistent with those of deadwood necromass

Research on decomposer communities has traditionally focused on plant litter or deadwood. Even though carrion forms highly nutrient-rich necromass that enhance ecosystem heterogeneity, the factors influencing saprophytic communities remain largely unknown. For deadwood, experiments have shown that different drivers determine beetles (i.e., decay stage, microclimate, and space), fungi (i.e., decay stage and tree species) and bacteria (decay stage only) assemblages. To test the hypothesis that similar factors also structure carrion communities, we sampled 29 carcasses exposed for 30 days that included Cervus elaphus (N = 6), Capreolus capreolus (N = 18), and Vulpes vulpes (N = 5) in a mountain forest throughout decomposition. Beetles were collected with pitfall traps, while microbial communities were characterized using amplicon sequencing. Assemblages were determined with a focus from rare to dominant species using Hill numbers. With increasing focus on dominant species, the relative importance of carcass identity on beetles and space on bacteria increased, while only succession and microclimate remained relevant for fungi. For beetle and bacteria with focus on dominant species, host identity was more important than microclimate, which is in marked contrast to deadwood. We conclude that factors influencing carrion saprophytic assemblages show some consistency, but also differences from those of deadwood assemblages, suggesting that short-lived carrion and long-lasting deadwood both provide a resource pulse with different adaptions in insects and microbes. As with deadwood, a high diversity of carcass species under multiple decay stages and different microclimates support a diverse decomposer community.

Characterization of Bacillus anthracis replication and persistence on environmental substrates associated with wildlife anthrax outbreaks

Anthrax is a zoonosis caused by the environmentally maintained, spore-forming bacterium Bacillus anthracis, affecting humans, livestock, and wildlife nearly worldwide. Bacterial spores are ingested, inhaled, and may be mechanically transmitted by biting insects or injection as occurs during heroin-associated human cases. Herbivorous hoofstock are very susceptible to anthrax. When these hosts die of anthrax, a localized infectious zone (LIZ) forms in the area surrounding the carcass as it is scavenged and decomposes, where viable populations of vegetative B. anthracis and spores contaminate the environment. In many settings, necrophagous flies contaminate the outer carcass, surrounding soils, and vegetation with viable pathogen while scavenging. Field observations in Texas have confirmed this process and identified primary browse species (e.g., persimmon) are contaminated. However, there are limited data available on B. anthracis survival on environmental substrates immediately following host death at a LIZ. Toward this, we simulated fly contamination by inoculating live-attenuated, fully virulent laboratory-adapted, and fully virulent wild B. anthracis strains on untreated leaves and rocks for 2, 5, and 7 days. At each time point after inoculation, the number of vegetative cells and spores were determined. Sporulation rates were extracted from these different time points to enable comparison of sporulation speeds between B. anthracis strains with different natural histories. We found all B. anthracis strains used in this study could multiply for 2 or more days post inoculation and persist on leaves and rocks for at least seven days with variation by strain. We found differences in sporulation rates between laboratory-adapted strains and wild isolates, with the live-attenuated strain sporulating fastest, followed by the wild isolates, then laboratory-adapted virulent strains. Extrapolating our wild strain lab results to potential contamination, a single blow fly may contaminate leaves with up to 8.62 x 105 spores per day and a single carcass may host thousands of flies. Replication outside of the carcass and rapid sporulation confirms the LIZ extends beyond the carcass for several days after formation and supports the necrophagous fly transmission pathway for amplifying cases during an outbreak. We note caution must be taken when extrapolating replication and sporulation rates from live-attenuated and laboratory-adapted strains of B. anthracis.

Factors Affecting the Composition and Succession of Beetles in Exposed Pig Carcasses in Southern Brazil

Coleoptera is one of the largest taxon among animals and exhibits diverse eating habits. When associated with decaying corpses, beetles can be of great value in estimating the postmortem interval. In order to consolidate a useful database for the forensic field, it is necessary to study the entomological fauna associated with the carcasses in different geographical regions since the diversity of insects varies according to the biogeoclimate zone. Thus, this study aimed to assess the influence of environmental and ecological factors on the composition and succession of beetles associated with pig carcasses exposed in southern Brazil. Collections were carried out during the hot/dry and cold/wet seasons. A total of 415 specimens belonging to 18 Coleoptera families were sampled. The highest total abundance (n = 329) and diversity (n = 44 taxa) were recorded in the cold/wet season, corresponding to approximately 80% of the total sampled from the two seasons. Dermestidae (26.7%) was the family most abundantly sampled. Regarding eating habits, in an increasing order of importance were necrophagous (43.3%), predator (31.6%), and omnivorous (0.05%). In the hot/dry season, there was no faunal succession. In the cold/wet season, the succession was more associated with differences in abundance than to the presence or absence of a specific taxon by decomposition stage. Considering all the factors analyzed in the current study, three species of beetles, Dermestes maculatus DeGeer (Dermestidae), Euspilotus azureus (Sahlberg, 1823) (Histeridae), and Oxelytrum discicolle Brullé, 1840 (Silphidae), could be identified as being of the greatest forensic relevance in this biogeoclimatic zone.

Biological, Ecological, and Distributional Aspects of Two Native Species of Lucilia Genus (Diptera: Calliphoridae) of Forensic Interest in Yungas Environments of Argentina

This study determined the spatial and temporal dynamics of two native neotropical species flies of forensic interest, belonging to the Lucilia (Robineau-Desvoidy) genus. The study focused on their abundance and reproductive behaviors associated with different habitats and phenological parameters. In the Province of Salta, Argentina, monthly samplings were performed over 1 yr in urban, rural, and native habitats, at morning, mid-day, and afternoon periods, controlling the oviposition of captured specimens. Environmental variables were also assessed: cloudiness, precipitation, relative humidity, temperature, and tree cover. Lucilia purpurascens (Walker) appeared to be associated with native habitats, whereas Lucilia ochricornis (Wiedemann) was mainly associated with rural habitats, exhibiting distinct habitat preferences. Two ecotones were also identified: rural-urban and rural-native, suggesting rural habitats promoted habitable conditions at its margins. Both species were recorded at the end of winter to the middle of autumn, with an initial peak in early spring, and a second peak at late summer. These peaks were associated with the highest numbers of laid eggs. Lucilia purpurascens preferred high tree coverings, whereas L. ochricornis resisted areas with intermediate sun, suggesting limited sun exposure was important. The latter was also associated with daily flight activities; during the warm season, the densest catches occurred at morning and afternoon periods, whereas during the cold season, they occurred at mid-day. Climatic variables explained 77% of variability in terms of abundance and oviposition. Synergistic effects were observed between these variables, suggesting that these variables conditioned insect distribution and reproduction, and not just temperature per se.

A review of experimental design in forensic taphonomy: moving towards forensic realism

Forensic taphonomy as a discipline requires standardization to satisfy Daubert criteria for scientific data to be admissible in court. In response, there has been a shift towards quantification of methodology and estimating the postmortem interval. Despite these advances, there are still biases and limitations within the discipline not explicitly addressed in the early stages of experimental design nor in final published works. In this article, unresolved debates with respect to the conductance and reporting of forensic taphonomic research are reviewed, beginning with the nature of experimental cadavers, human or animal analogues and their body size, and second, the forensic realism of experimental setups, specifically with respect to caging, clothing and number of carcases. Pigs, albeit imperfect, are a good model to gain a general idea of the trends that may be seen in humans in subsequent validation studies in facilities where human donors are available. To date, there is no consensus among taphonomists on the extent of the effect that body mass has on decomposition progression. More research is required with both human cadavers and non-human analogues that builds on our current knowledge of forensic taphonomy to answer these nagging questions. This will enable the discipline to make the reliable assumption that pigs and donor decomposition data can be applied to homicide cases. A suite of experimental design aspects is suggested to ensure systematic and standardized data collection across different biogeoclimatic circumstances to identify and quantify the effects of potential confounding variables. Such studies in multiple, varied biogeographic circumstances with standardized protocols, equipment and carrion will facilitate independent global validation of patterns. These factors are reviewed to show the need for adjustments in experimental design to ensure relevance and applicability of data within locally realistic forensic situations. The initiation of a global decomposition data network for forensic taphonomists is recommended.

Key points

Pigs are a valuable, albeit imperfect, proxy for human decomposition studies.

There are few or conflicting data on effects of carcase size, carrion ecology, exclusion cages and scavengers.

We recommend single, clothed, uncaged carcases for baseline research to reflect regionally specific forensic casework.

Molecular characterization of gut microbial shift in SD rats after death for 30 days

To observe the temporal shifts of the intestinal microbial community structure and diversity in rats for 30 days after death. Rectal swabs were collected from rats before death (BD) and on day 1, 5, 10, 15, 20, 25, and 30 after death (AD). Bacteria genomic DNA was extracted and V3 + V4 regions of 16S rRNA gene were amplified by PCR. The amplicons were sequenced at Illumina MiSeq sequencing platform. The bacterial diversity and richness showed similar results from day 1 to 5 and day 10 to 25 all presenting downtrend, while from day 5 to 10 showed slightly increased. The relative abundance of Firmicutes and Proteobacteria displayed inverse variation in day 1, 5, 10 and that was the former decreased, the latter increased. Bacteroidetes, Spirochaete and TM7 in day 15, 20, 25, 30 was significantly decline comparing with BD. Enterococcus and Proteus displayed reduced trend over day 1, 5, 10 and day 10, 15, 20, 25, respectively, while Sporosarcina showed obvious elevation during day 15, 20, 25. Accordingly, there was a certain correlation between intestinal flora succession and the time of death. The results suggested that intestinal flora may be potential indicator to aid estimation of post-mortem interval (PMI).

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.

Two human cases associated with forensic insects in Riyadh, Saudi Arabia

In Riyadh, Saudi Arabia, we are reporting two cases of natural death. The two bodies showed different types of habitat, insect colonization and decomposition stage. The first case was about the body of a 65-years-old male, with mummification of the clothed body was found in an outdoor habitat. Different life stages of Dermestes maculatus DeGeer (Coleoptera: Dermestidae were gathered from the cadaver, and due to the advanced degree of decomposition, the PMImin was estimated to be 3 months. The second body belonging to a 40-years-old male, was found in a semi-closed apartment (indoor habitat), and the body was at the end of the bloated decomposition stage. In this case, Musca domestica L. (Diptera: Muscidae) larvae were collected, and the PMImin was estimated to be 4 days. The limited insect activity for the two bodies caused by the advanced decomposition stage in the first case and indoor environment in the second. Average temperatures of (23.3 ± 1.6) °C for the first body and (27.5 ± 1.7) °C2 for the second body. Habitat was the key factor to attract insects to the two cadavers. This study stressed that, for accurate estimates of time since death, knowledge of the impact of different variables on insects found over and around the carrion is essential.

Necrophagous Fly Assembly: Evaluation of Species Bait Preference in Field Experiments

The assembly of species that colonize animal organic matter, their relative abundance, and dynamics are affected by the environmental and biogeographical conditions to which these resources are exposed. Baited trap studies are essential for research on the diversity, seasonality, distribution and population dynamics of necrophagous flies. Decomposing baits provide the necessary stimulus for flies to aggregate on them. In this study, three types of bait of animal origin with different organic chemical composition were compared in terms of the diversity, richness, abundance, and species composition of saprophagous flies species that were attracted to them. Bone-meal (BM), cow liver (CL), and rotten chicken viscera (CV) were used as bait to collect flies. In total, 3,387 Calliphoridae, Sarcophagidae, and Muscidae adult flies were collected. The most abundant species were Lucilia ochricornis (Wiedemann 1830), Chrysomya albiceps (Wiedemann 1819) (Diptera: Calliphoridae), Peckia (Sarcodexia) lambens (Wiedemann 1830) (Diptera: Sarcophagidae), and Ophyra capensis (Wiedemann 1818) (Diptera: Muscidae). The type of bait had significant effects on both the total richness (F2,18 = 57.08; P < 0.0001) and the effective number of species (F2,18 = 12.81; P = 0.0003) per trap. The average richness was higher in traps baited with chicken viscera, followed by cow liver and finally by bone-meal. The composition of cow liver and bone meal species constitute subsets of the species collected with chicken viscera, thus using the three baits would not increase the number of species detected. These results indicate that chicken viscera is the most efficient bait for testing or assessing necrophagous fly diversity.

A serine protease-associated lectin in the cytolytic system of blowfly (Chrysomya megacephala) larvae: Evidence and characterization

Cytolytic activity against invading microorganisms is one of the innate forms of immunity in invertebrates. A serine protease-associated sialic acid-specific cytolytic lectin was purified using glutaraldehyde-fixed ox erythrocytes from the larval extract of blowfly (Chrysomya megacephala). The purified lectin lysed vertebrate erythrocytes with effective haemolysis of ox red blood cells (RBCs) in an isotonic medium. The degree of haemolytic (HL) activity of the purified cytolytic lectin depended on its concentration, pH, temperature, and calcium ions. It was sensitive to ethylenediaminetetraacetic acid. The native molecular mass of the C-type lectin was 260 ± 26 kDa, comprising four different polypeptide subunits of 75 kDa (pI ~8), 69 kDa (pI ~7.0), 61 kDa (pI ~5.3), and 55 kDa (pI ~4.6). The association between the C-type lectin and serine protease was confirmed by MALDI-TOF-MS analysis that revealed its homology in the same spectral peak as well as the proteases and phenylmethylsulphonyl fluoride inhibition of HL activity. Haemolysis inhibition by N-acetylneuraminic acid and other sugars revealed the properties of the lectin. The purified lectin distorted the integrity of ox RBCs and Paenalcaligenes hermetiae. This in vitro study documents the presence of a cytolytic system in blowfly (C. megacephala) larvae for the clearance of invading microbial pathogens in their feeding niche.

Scavenging Activity of Dermestes maculatus (Coleoptera: Dermestidae) on Burned Cadaveric Tissue

The aim of this work was to study the effect that fire exposure in tissues may have on Dermestes maculatus DeGeer (Dermestidae: Dermestini) taphonomic behaviour under controlled conditions. Two different times of fire exposure (treatments) were evaluated, 15 min and 30 min, after spraying pig trotters with gasoil. The pig trotters were provided to adult hide beetles and both were maintained at 24 ± 0.1°C, 55.4% ± 2% relative humidity, and a 12:12 h day/night cycle. An unburned pig trotter was used as a control for each treatment. Observations were made and photographs were taken every 4-5 days for 4 months. Qualitative and quantitative analyses were performed. Dermestes maculatus was able to feed and reproduce on burned tissues. Beetles in adult and larvae stages produced different types of marks in several kinds of tissues such as integumental, connective, and muscular, in the controls and treatments. Apparently, 15 min of burning the pig trotters were not sufficient enough to cause differences in the taphonomic marks with respect to the control, but post mortem burning for 30 min may have implicated changes (lesser insect damage represented by lesser number and surface of both depressions and holes were found with respect to the control; greater surfaces and diameters were noticed compared to those found in the unburned pig trotters). The shape of the marks was equal in the controls and treatments.

Estimating the Age of Forensically Useful Blowfly, Sarconesia chlorogaster (Diptera: Calliphoridae), Using Larval Length and Weight

Determining the age of an insect collected in a corpse is a key element to estimate the minimum postmortem interval in forensic entomology. Along with models of accumulated degree-hours, the estimation of the age based on larval weight and length is among the most common methods for this purpose. Sarconesia chlorogaster (Wiedemann, 1830), along with other Calliphoridae, is an important species in forensics in South America. However, studies analyzing the weight and length of S. chlorogaster larvae during development have not yet been done. In this work, we develop growth models based on the weight and length of larvae in different temperatures and provide formulas that can be used to estimate the age of the larvae based on the weight and length for each temperature. Larvae were reared at six temperatures (10, 15, 20, 25, 30, 35°C), and the measurements of larval length and weight were taken during all development until they stopped feeding. For the measurements, we attempted to use methodologies that can be easily replicated and do not require equipment that could be of difficult access. The results of this work come to complement and improve the use of S. chlorogaster in forensic applications.

Forensic entomology application in China: Four case reports

We present four cases that use entomological data to estimate postmortem interval (PMI). In the first case, the body was found in an outdoor environment at 26 °C and was at the fresh stage. However, the PMI_min estimated using maggots collected from the corpse was more than 68 h. This was certainly an incorrect estimation because the degree of the body decomposition was light, and it may have been caused by flies invading the corpse before death occurred. In the second case, a corpse of an adult male was found in a semi-closed room, and the body was highly decomposed and mummified. In this case, we used Dermestes maculatus DeGeer (Coleoptera: Dermestidae) to successfully estimate the PMI. The third case involved a female body discovered in her room after she committed suicide by consuming excessive clozapine and alcohol. The PMI_min estimated through entomological data did not match the time of death that the other evidence indicated. Thus, we speculated that clozapine and alcohol may have influenced the development of fly larvae. The fourth case occurred in the winter. The murderer killed the victim and burned and dumped the corpse. However, the burned body still attracted necrophagous insects and we successfully calculated the PMI_min by using insect evidence.

Depressions of Dermestes maculatus (Coleoptera: Dermestidae) on Bones Could be Pupation Chambers

Dermestes maculatus DeGeer beetles feed and can leave marks on bones. This species is of medical, veterinary, and forensic importance. The aim of this work was to determine if the depressions produced on bones by these beetles could be product of pupation. We studied under controlled conditions the behavior of D. maculatus larvae maintained at 24°C ± 3°C, 52.7% average relative humidity, and a 12:12-hour light/dark cycle and fed on pig carcasses. Observations were made, and photographs were taken. The results indicated that depressions produced by D. maculatus were consequence of feeding or pupation. This is the first time that pupation chambers on bones are confirmed.

Differential Decomposition Among Pig, Rabbit, and Human Remains

While nonhuman animal remains are often utilized in forensic research to develop methods to estimate the postmortem interval, systematic studies that directly validate animals as proxies for human decomposition are lacking. The current project compared decomposition rates among pigs, rabbits, and humans at the University of Tennessee's Anthropology Research Facility across three seasonal trials that spanned nearly 2 years. The Total Body Score (TBS) method was applied to quantify decomposition changes and calculate the postmortem interval (PMI) in accumulated degree days (ADD). Decomposition trajectories were analyzed by comparing the estimated and actual ADD for each seasonal trial and by fuzzy cluster analysis. The cluster analysis demonstrated that the rabbits formed one group while pigs and humans, although more similar to each other than either to rabbits, still showed important differences in decomposition patterns. The decomposition trends show that neither nonhuman model captured the pattern, rate, and variability of human decomposition.

Different feeding strategies in Antarctic scavenging amphipods and their implications for colonisation success in times of retreating glaciers

Background

Scavenger guilds are composed of a variety of species, co-existing in the same habitat and sharing the same niche in the food web. Niche partitioning among them can manifest in different feeding strategies, e.g. during carcass feeding. In the bentho-pelagic realm of the Southern Ocean, scavenging amphipods (Lysianassoidea) are ubiquitous and occupy a central role in decomposition processes. Here we address the question whether scavenging lysianassoid amphipods employ different feeding strategies during carcass feeding, and whether synergistic feeding activities may influence carcass decomposition. To this end, we compared the relatively large species Waldeckia obesa with the small species Cheirimedon femoratus, Hippomedon kergueleni, and Orchomenella rotundifrons during fish carcass feeding (Notothenia spp.). The experimental approach combined ex situ feeding experiments, behavioural observations, and scanning electron microscopic analyses of mandibles. Furthermore, we aimed to detect ecological drivers for distribution patterns of scavenging amphipods in the Antarctic coastal ecosystems of Potter Cove. In Potter Cove, the climate-driven rapid retreat of the Fourcade Glacier is causing various environmental changes including the provision of new marine habitats to colonise. While in the newly ice-free areas fish are rare, macroalgae have already colonised hard substrates. Assuming that a temporal dietary switch may increase the colonisation success of the most abundant lysianassoids C. femoratus and H. kergueleni, we aimed to determine their consumption rates (g food x g amphipods⁻¹ x day⁻¹) and preferences of macroalgae and fish.

Results

We detected two functional groups with different feeding strategies among scavenging amphipods during carcass feeding: carcass ‘opener’ and ‘squeezer’. Synergistic effects between these groups were not statistically verified under the conditions tested. C. femoratus switched its diet when fish was not available by consuming macroalgae (about 0.2 day⁻¹) but preferred fish by feeding up to 80% of its own mass daily. Contrary, H. kergueleni rejected macroalgae entirely and consumed fish with a maximal rate of 0.8 day⁻¹.

Conclusion

This study reveals functional groups in scavenging shallow-water amphipods and provides new information on coastal intraguild niche partitioning. We conclude that the dietary flexibility of C. femoratus is a potential ecological driver and central to its success in the colonisation of newly available ice-free Antarctic coastal habitats.

Electronic supplementary material

The online version of this article (10.1186/s12983-017-0248-3) contains supplementary material, which is available to authorized users.

New records of forensic entomofauna in legally buried and exhumed human infants remains in Buenos Aires, Argentina

The study of carrion fauna associated with buried human corpses from a forensic perspective could provide useful information in criminal investigations. Insects and other arthropods remains sampled of 44 legally exhumed infant skeletons from La Plata (Buenos Aires, Argentina). They were identified at different taxonomic levels depending on the state of preservation. The specific diversity, abundance and frequency were analyzed and each taxon was assigned to the hypothetical colonization sequence: burial colonization, post-exhumation contamination at cemetery deposit or soil fauna. The phorid Dohrniphora sp. is mentioned for the first time in Argentina as carrion fauna of underground colonization, and the assemblage of Dohrniphora sp., Megaselia scalaris and Hydrotaea aenescens is proposed as indicator of buried cadavers. These findings provide new useful data to be applied in forensic entomology research.

Use of necrophagous insects as evidence of cadaver relocation: myth or reality?

The use of insects as indicators of post-mortem displacement is discussed in many texts, courses and TV shows, and several studies addressing this issue have been published. Although the concept is widely cited, it is poorly understood, and only a few forensic cases have successfully applied such a method. The use of necrophagous insects as evidence of cadaver relocation actually involves a wide range of biological aspects. Distribution, microhabitat, phenology, behavioral ecology, and molecular analysis are among the research areas associated with this topic. This article provides the first review of the current knowledge and addresses the potential and limitations of different methods to evaluate their applicability. This work reveals numerous weaknesses and erroneous beliefs as well as many possibilities and research opportunities.

Chemotaxonomic Profile and Intraspecific Variation in the Blow Fly of Forensic Interest Chrysomya megacephala (Diptera: Calliphoridae)

Necrophagous insects such as blow flies (Diptera: Calliphoridae) are considered crucial in forensic entomology. Identification at species level and determination of larval stage are the basis for estimation of postmortem interval (PMI). Insect evidence can also be used in the determination of crime scenes, since body displacement is common. The aim of this study was to determine the chemotaxonomic profile and intraspecific variability of the forensically important blow fly Chrysomya megacephala (F. 1794). Adults were collected in the municipalities of Dourados-MS (Brazil) and Rio Claro-SP (Brazil), and then transferred to the laboratory for oviposition and development of the immature stages. Chemical analysis of cuticular compounds was performed by gas chromatography. Cuticular chemical profiles varied significantly between the two populations, as well as between developmental stages, supporting the use of these compounds as a complementary tool to help identify the species and its stages, along with geographical variability. This could greatly accelerate forensic investigations, eliminating the need to allow the fly larvae to develop until adult stage in order to confirm the species identity and sample origin.

Diptera of Medico-Legal Importance Associated With Pig Carrion in a Tropical Dry Forest

The diversity of necrophagous Diptera is largely unknown in seasonally dry tropical forests, despite their medical, veterinary, and forensic relevance. We performed a study in the dry Caatinga forest exclusive to Brazil in order to assess the diversity and temporal pattern of Diptera species using pig carcasses as substrates. Adults were collected daily until complete skeletonization. We collected 17,142 adults from 18 families, 10 of which comprise species with known necrophagous habits. The most abundant families were Calliphoridae (47.3% of specimens), Sarcophagidae (20.8%), and Muscidae (15.5%), whereas Sarcophagidae stood out in terms of richness with 21 species. The native Cochliomyia macellaria (F.) (Diptera: Calliphoridae) and the invasive Chrysomya albiceps (Wiedmann) (Calliphoridae) were the dominant species. A total of 18 species reached the carcass during the first 48 h postdeath. The bloated and active decay stages had the highest richness and abundance of dipterans. From a forensic standpoint, C. macellaria and C. albiceps are likely to aid in establishing postmortem interval due to their early arrival and high abundance on the carcass. Despite harsh environmental conditions, the Caatinga harbors a rich assemblage of dipterans that play a key role in carrion decomposition. Their medico-veterinary importance is strengthened by the poor local sanitary conditions.

Volatile Organic Compounds of Decaying Piglet Cadavers Perceived by Nicrophorus vespilloides

In the necrophagous burying beetle Nicrophorus vespilloides (Coleoptera: Silphidae), cadaver preference appears to depend on cadaver size and on the maturity of the beetle. We previously showed that newly emerged females with immature ovaries prefer later stages of decomposition of large cadavers. Our present aim is the determination of specific chemical compounds involved in the discrimination of cadaveric odor bouquets and the recognition of specific stages of decomposition. We used headspace samples of maggot-infested piglet cadavers at various decomposition stages and performed gas chromatography coupled with electroantennography (GC-EAD) to record 45 EAD-active compounds. Using GC coupled with mass spectrometry, we identified 13 of the EAD-active compounds. The headspace of the fresh decomposition stage was characterized mainly by high relative amounts of trimethylpyrazine. High relative amounts of dimethyl trisulfide were characteristic of bloated, post-bloating, and advanced decay stages. The advanced decay and dry remains stages were dominated by high relative amounts of phenol. Statistically, this compound had the highest impact on discrimination between the fresh decomposition stage, which is important for mature burying beetles for reproduction, and the advanced decay stage, which is nutritionally more attractive for newly emerged beetles. Phenol might, therefore, function as a key substance for newly emerged female burying beetles, so that they can locate suitable cadavers for feeding to maturation.

Active Search on Carcasses versus Pitfall Traps: a Comparison of Sampling Methods

The study of insect succession in cadavers and the classification of arthropods have mostly been done by placing a carcass in a cage, protected from vertebrate scavengers, which is then visited periodically. An alternative is to use specific traps. Few studies on carrion ecology and forensic entomology involving the carcasses of large vertebrates have employed pitfall traps. The aims of this study were to compare both sampling methods (active search on a carcass and pitfall trapping) for each coleopteran family, and to establish whether there is a discrepancy (underestimation and/or overestimation) in the presence of each family by either method. A great discrepancy was found for almost all families with some of them being more abundant in samples obtained through active search on carcasses and others in samples from traps, whereas two families did not show any bias towards a given sampling method. The fact that families may be underestimated or overestimated by the type of sampling technique highlights the importance of combining both methods, active search on carcasses and pitfall traps, in order to obtain more complete information on decomposition, carrion habitat and cadaveric families or species. Furthermore, a hypothesis advanced on the reasons for the underestimation by either sampling method showing biases towards certain families. Information about the sampling techniques indicating which would be more appropriate to detect or find a particular family is provided.

Review of Postmortem Interval Estimation Using Vitreous Humor: Past, Present, and Future

For decades, forensic scientists have sought a means of estimating the postmortem interval using laboratory analyses. The best known of these attempts uses a linear regression formula based on the increasing concentration of potassium ions in vitreous humor following death. Like all laboratory analyses, the determination of a potassium concentration is subject to pre-analytical, analytical, and post-analytical errors. Any error is magnified when entered into a regression formula that itself is subject to statistical variation, typically with a 95% confidence interval. Estimating the postmortem interval based solely on the concentration of potassium in vitreous humor proved too simplistic for accurate modeling of the myriad factors that influence postmortem changes. Research continues, using more complicated algorithms involving multivariate ion and chemical analyses and genomic sequencing of the postmortem biome. However refined estimates of the postmortem interval based on laboratory analysis become, sound medical practice will still require the integration of scene findings and information concerning the last time that a given decedent was known to be alive with the results of postmortem examination and laboratory analyses into a medical opinion concerning the postmortem interval.

Unusual presence of Ornidia robusta (Diptera: Syrphidae) causing pig myiasis in Argentina

Myiasis is caused by dipterous larvae from the Calliphoridae, Sarcophagidae, Muscidae, Cuterebridae, and Syrphidae families. In this work, Cochliomyia hominivorax, Chrysomya megacephala, and Ornidia robusta were identified causing vulva, ear, and leg myiasis in pigs in Tucuman province, northwestern Argentina. The report of the presence of C. hominivorax and C. megacephala is very important due to their role as myiasis-causing and disease vectors. The occurrence of Ornidia robusta is remarkable, since it constitutes the first record of myiasis in general and of myiasis in pigs in particular. Lastly, the presence of Sarcophaga spp. is also interesting, since some of them originate myiasis and are therefore of concern for cattle, wild animals, and human populations.

A Biological and Procedural Review of Forensically Significant Dermestes Species (Coleoptera: Dermestidae)

The analyses of the insect species found on decomposing remains may provide useful information for the estimation of the minimum time elapsed since death and other parameters, such as causes and circumstances of death. The majority of research has focused on the early colonizing species, typically blowflies, while research concerning late colonizing insects is currently sparse. Dermestid beetles of the genus Dermestes L. (Coleoptera: Dermestidae) are one of the predominant insect species associated with decomposing remains during dry decay and skeletal stages of decomposition. In some dry environments, Dermestes species are likely to be the only necrophagous insects feeding on the decomposing remains. Furthermore, Dermestes species (immature and adults), their remains (cast skins and fecal material), and their artifacts (pupal chambers) are frequently found associated with ancient remains (e.g., mummies, fossils). Dermestes species have a worldwide distribution and are considered important in decomposition processes, forensic investigations, and economically as a known pest of stored products. Despite their recognized forensic importance, there is limited data documenting the ecology, biology, and the growth rates of the forensically relevant species. The aim of this review is to provide a comprehensive synopsis on the available literature concerning Dermestes species associated with forensic cases. In particular, aspects of colonization behavior, growth rates for forensic taxa and potential best practice guidelines for forensic casework encompassing late colonizing Dermestes species are discussed.

Thermal requirements of Ophyra albuquerquei Lopes, 1985 (Diptera, Muscidae)

This study determines the development rates of the immature stages of the fly Ophyra albuquerquei Lopes, 1985. In this study, with 70% relative humidity and a 12-h photophase, eggs, larvae, and pupae were kept in a biochemical oxygen demand chamber at temperatures of 10, 15, 17, 20, 22, 25, 27, 30, 33, 35, and 40°C. While the rearing temperature increases, the development time for each immature stage of O. albuquerquei decreases and these stages develop at temperatures from 10 to 35°C. For eggs, the average minimum development time was 16h, and the average maximum development time was 81h. The average minimum development time for larvae and pupae was 7 and 6 days, respectively, and the average maximum development time was 22 and 42 days, respectively. To understand the development rate of each immature stage of the fly, a mathematical model is presented.

Comparative study of mitotic chromosomes in two blowflies, Luciliasericata and L.cluvia (Diptera, Calliphoridae), by C- and G-like banding patterns and rRNA loci, and implications for karyotype evolution

The karyotypes of Luciliacluvia (Walker, 1849) and Luciliasericata (Meigen, 1826) from Argentina were characterized using conventional staining and the C- and G-like banding techniques. Besides, nucleolus organizer regions (NORs) were detected by fluorescent in situ hybridization (FISH) and silver staining technique. The chromosome complement of these species comprises five pairs of autosomes and a pair of sex chromosomes (XX/XY, female/male). The autosomes of both species have the same size and morphology, as well as C- and G-like banding patterns. The X and Y chromosomes of Luciliacluvia are subtelocentric and easily identified due to their very small size. In Luciliasericata, the X chromosome is metacentric and the largest of the complement, showing a secondary constriction in its short arm, whereas the Y is submetacentric and smaller than the X. The C-banding patterns reflect differences in chromatin structure and composition between the subtelocentric X and Y chromosomes of Luciliacluvia and the biarmed sex chromosomes of Luciliasericata. These differences in the sex chromosomes may be due to distinct amounts of constitutive heterochromatin. In Luciliacluvia, the NORs are placed at one end of the long-X and of the long-Y chromosome arms, whereas one of the NORs is disposed in the secondary constriction of the short-X chromosome arm and the other on the long-Y chromosome arm in Luciliasericata. Although the G-like banding technique does not yield G-bands like those in mammalian chromosomes, it shows a high degree chromosomal homology in both species because each pair of autosomes was correctly paired. This chromosome similarity suggests the absence of autosomal rearrangements during karyotype evolution in the two species studied.

First record of genus Puliciphora Dahl (Diptera: Phoridae) associated with rabbit carcasses placed in concealed environments in Malaysia

Scuttle flies of genus Puliciphora Dahl (Diptera: Phoridae) are recorded for the first time in Malaysia from rabbit carcasses placed in concealed environments. They consist of Puliciphora borinquenensis Wheeler ♂♀, Puliciphora obtecta Meijere ♀ and Puliciphora beckeri Meijere ♀. All species were obtained from rabbit carcasses in used luggage and garbage bin placed at Forensic Science Simulation Site, Universiti Kebangsaan Malaysia, Bangi, Selangor. The specimens were collected from the carcasses using a modified Malaise trap, an entomological aspirator and preserved in 70% ethanol. This report expands the geographical distributions of these species and their microhabitat, suggests its possible important role in forensic entomology.

The immature stages of Dermestes maculatus, Sarcophaga sp. and Phaenicia sericata as potential paratenic hosts for Trichinella spiralis in nature

The role of some insect populations in the transmission of Trichinella sp. has been demonstrated. However, most of the studies have been conducted under controlled conditions which may influence the real role that they could play as a paratenic host in nature. To enlight this issue, a series of studies to determine the infective capability of the muscle larva of Trichinella spiralis recovered from immature stages of insect populations that fed on infected tissues exposed to natural conditions were carried out. Mice harbouring T. spiralis muscle larvae (ML) were sacrificed and deposited on a pitfall trap which was established in an open and safe area through 25 days in summer. Necrophilous and necrophagous insects that fed on corpses were recovered, identified and processed to search for live ML of T. spiralis. A complementary study in which maggots of Dermestes maculatus recovered from nature were induced to feed on muscle tissues harbouring T. spiralis larvae was also performed. The muscle larvae recovered from insects at different times of exposition were counted and inoculated to mice to determine the reproductive capability index (RCI). At day 3 of exposition, 29 live ML of T. spiralis were recovered from maggots of Phaenicia sericata. The RCI for these larvae was 133.6. On day 5 of exposition, maggots of Sarcophaga sp. were identified and 17 live T. spiralis larvae were recovered; the RCI of these larvae was 43.4. The T. spiralis ML recovered from maggots of D. maculatus obtained after 2 days of feeding on experimentally infected tissue showed a RCI of 24. The results suggest that larval stages of P. sericata, Sarcophaga sp. and D. maculatus might have an important role as a paratenic host of T. spiralis, which, in terms, may influence the epidemiology of this nematode in endemic areas of trichinellosis.

Report on the occurrence of synanthropic derived form of Chrysomyamegacephala (Diptera: Calliphoridae) from Royapuram fishing harbour, Chennai, Tamil Nadu, India

The occurrence of dipteran fly, Chrysomyamegacephala (Fabricius, 1794) is reported for the first time from Royapuram fishing harbour (Chennai), Tamil Nadu, South East India. The fully grown third instar larvae of Chrysomyamegacephala were collected from decaying fishes near Royapuram fishing harbour. This site is found to be the regular breeding site for Chrysomyamegacephala. Larvae were reared under laboratory condition and freshly emerged adult flies from pupae were collected and identified by morphological features and molecular tools. Molecular identification through generation of DNA barcoding using mitochondrial COI gene of Chrysomyamegacephala is appended.