Coleoptera of forensic interest: a study of seasonal community composition and succession in Lisbon, Portugal

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.

Ecological drivers of carrion beetle (Staphylinidae: Silphinae) diversity on small to large mammals

Silphinae (Staphylinidae; carrion beetles) are important contributors to the efficient decomposition and recycling of carrion necromass. Their community composition is important for the provision of this ecosystem function and can be affected by abiotic and biotic factors. However, investigations are lacking on the effects of carrion characteristics on Silphinae diversity. Carrion body mass may affect Silphinae diversity following the more individuals hypothesis (MIH). The MIH predicts a higher number of species at larger carrion because higher numbers of individuals can be supported on the resource patch. Additionally, biotic factors like carrion species identity or decomposition stage, and the abiotic factors elevation, season and temperature could affect Silphinae diversity. To test the hypotheses, we collected Silphinae throughout the decomposition of 100 carcasses representing 10 mammal species ranging from 0.04 to 124 kg. Experimental carcasses were exposed in a mountain forest landscape in Germany during spring and summer of 2021. We analysed Silphinae diversity using recently developed transformation models that considered the difficult data distribution we obtained. We found no consistent effect of carrion body mass on Silphinae species richness and, therefore, rejected the MIH. Carrion decomposition stage, in contrast, strongly influenced Silphinae diversity. Abundance and species richness increased with the decomposition process. Silphinae abundance increased with temperature and decreased with elevation. Furthermore, Silphinae abundance was lower in summer compared to spring, likely due to increased co-occurrence and competition with dipteran larvae in summer. Neither carrion species identity nor any abiotic factor affected Silphinae species richness following a pattern consistent throughout the seasons. Our approach combining a broad study design with an improved method for data analysis, transformation models, revealed new insights into mechanisms driving carrion beetle diversity during carrion decomposition. Overall, our study illustrates the complexity and multifactorial nature of biotic and abiotic factors affecting diversity.

Temperature-Dependent Development of Nitidula rufipes (Linnaeus, 1767) (Coleoptera: Nitidulidae) and Its Significance in Estimating Minimum Postmortem Interval

Coleoptera, including the family Nitidulidae, are valuable for estimating long-term postmortem intervals in the late stage of body decomposition. This study showed that, under seven constant temperatures of 16, 19, 22, 25, 28, 31, and 34 °C, the developmental durations of Nitidula rufipes (Linnaeus, 1767) from oviposition to eclosion were 71.0 ± 4.4, 52.9 ± 4.1, 40.1 ± 3.4, 30.1 ± 2.1, 24.2 ± 2.0, 21.0 ±2.3, and 20.8 ± 2.4 days, respectively. The morphological indexes of body length, the widths of the head capsules, and the distance between the urogomphi of the larvae were measured in vivo. The regression model between larval body length and developmental durations was simulated for larval aging, and the head capsule width and the distance between the urogomphi at different instars were cluster-analyzed for instar discrimination. Based on the developmental durations, larval body length and thermal summation data were obtained, and the isomorphen diagram, isomegalen diagram, linear thermal summation models, and curvilinear Optim SSI models were established. The lower developmental threshold and thermal summation constant of N. rufipes evaluated by the linear thermal summation models were 9.65 ± 0.62 °C and 471.40 ± 25.46 degree days, respectively. The lower developmental thresholds, intrinsic optimum temperature, and upper lethal developmental threshold obtained by Optim SSI models were 10.12, 24.15, and 36.00 °C, respectively. The study of the immature stages of N. rufipes can provide preliminary basic developmental data for the estimation of minimum postmortem interval (PMI_min). However, more extensive studies are needed on the effects of constant and fluctuating temperatures on the development of N. rufipes.

Ampliación de la distribución conocida de coleópteros, dípteros e himenópteros sarcosaprófagos (Arthropoda: Insecta) con potencial interés forense en la península ibérica

Con el objetivo de ampliar la distribución conocida y el conocimiento ecológico de las especies sarcosaprófagas con potencial interés forense en la península ibérica, se recopilan 758 nuevos registros correspondientes a 105 especies de coleópteros, dípteros e himenópteros en 43 provincias españolas y 4 distritos portugueses. Se registran un total de 89 primeras citas provinciales y se aportan numerosas localidades inéditas que permiten ampliar el rango de distribución conocido de la entomofauna sarcosaprófaga ibérica. Entre los resultados más relevantes destaca la expansión territorial de los dípteros alóctonos Chrysomya megacephala (Fabricius, 1794) y Hermetia illucens (Linnaeus, 1758) en la península ibérica. Además, se documentan hábitos sarcosaprófagos por primera vez en el formícido Hypoponera eduardi (Forel, 1894). Finalmente, se discuten los resultados ecológicos obtenidos en relación a las comunidades sarcosaprófagas y su potencial interés en estudios forenses.

Development of Necrobia ruficollis (Fabricius) (Coleoptera: Cleridae) under Different Constant Temperatures

Simple Summary

Sarcosaprophagous beetles are significant pests, but they are also key indicator insects for postmortem interval estimation. In this paper, the development of Necrobia ruficollis (Fabricius, 1775) at five constant temperatures between 22 °C and 34 °C was investigated. The developmental threshold temperature and thermal summation constant were estimated, the relationship between the larval body length with development time, and the widths of the head capsules and the distance between the urogomphi at different instars were studied. The results provide important basic developmental data for using N. ruficollis to estimate the minimum postmortem interval.

Abstract

Necrobia ruficollis (Fabricius, 1775) (Coleoptera: Cleridae) is an important cosmopolitan storage pest, and also frequently appears on highly decomposed and skeletonized corpses. It is a forensically important species expected to indicate a longer postmortem interval (PMI). Therefore, we investigated the development of N. ruficollis at five constant temperatures between 22 °C and 34 °C. Under temperatures of 22, 25, 28, 31, and 34 °C, the mean (±SD) developmental durations from eggs to adults were 93.00 ± 1.63, 70.67 ± 0.94, 65.33 ± 3.40, 47.33 ± 0.94, and 56.66 ± 8.73 days, respectively. According to the developmental time and accumulated degree hours results, an isomorphen diagram and thermal summation model were generated. The calculated values of developmental threshold temperature and accumulated temperature constant were estimated by a linear model to be 14.51 ± 0.52 °C and 684.12 ± 33.85 degree days, respectively. Lower developmental thresholds, intrinsic optimum temperature, and upper lethal developmental threshold temperature were estimated by a nonlinear model to be 14.61, 25.90, and 34.94 °C. Morphological indexes of larvae were obtained by in vivo measurements. A growth curve and an equation of the relationship between development time and body length were simulated. In addition, the widths of the head capsules and the distance between the urogomphi of larvae at different instars were determined by cluster analysis. Classifiers were created and validated by linear discriminant analysis. These results provide important basic developmental data for using N. ruficollis to estimate the minimum postmortem interval (minimum PMI). However, this study was only conducted under constant temperature, and the applicability of these data to variable temperature conditions needs to be further confirmed.

Insect abundance patterns on vertebrate remains reveal carrion resource quality variation

Resource quality is a key driver of species abundance and community structure. Carrion is unique among resources due to its high nutritional quality, rapidly changing nature, and the diverse community of organisms it supports. Yet the role resource quality plays in driving variation in abundance patterns of carrion-associated species remains poorly studied. Here we investigate how species abundances change with a measure of resource change, and interpret these findings to determine how species differ in their association with carrion that changes in quality over time. We conducted field succession experiments using pigs and humans over two winters and one summer. We quantified the effect of total body score, an objective measure of resource change, on adult insect abundance using generalised additive models. For each species, phases of increasing abundance likely indicated attraction to a high-quality resource, and length of abundance maxima indicated optimal oviposition and feeding time. Some species such as the beetle Necrobia rufipes had a rapid spike in abundance, suggesting a narrow window of opportunity for carrion resource exploitation, while species like the wasp Nasonia vitripennis had a gradual change in abundance, indicating a wide window of resource exploitation. Different abundance patterns were also observed between species occurring on pigs and humans, suggesting cadaver type is an important aspect of resource quality. Our findings show that species abundances, unlike species occurrences, can reveal additional detail about species exploitation of carrion and provide information about how resource quality may drive competition and variation in insect community succession.

Is Resource Change a Useful Predictor of Carrion Insect Succession on Pigs and Humans?

Carrion is a dynamic and nutrient-rich resource that attracts numerous insect species that undergo succession due to the rapid change in the carrion resource. Despite this process being well-understood, few studies have examined resource change as a driver of carrion insect succession, and instead have focused on the effects of time per se, or on coarse, qualitative measures such as decay stage. Here we report on three field succession experiments using pig carcasses and human cadavers encompassing two winters and one summer. We quantified the effects of resource change (measured as total body score, TBS), carrion type, initial carrion mass, ambient temperature, and season on insect species richness and community composition. We found that all variables had an effect on different taxonomic or trophic components of the insect community composition, with the exception of initial carrion mass which had no effect. We found significant positive effects of TBS on beetle species richness and composition, while fly species richness was not significantly affected by TBS, but was by ambient temperature. TBS had a significant positive effect on all trophic groups, while ambient temperature also had a significant positive effect on the necrophages and predator/parasitoids. Our study indicates that resource change, as indicated by TBS, is an important driver of carrion insect species turnover and succession on carrion, and that TBS can provide information about insect ecological patterns on carrion that other temporal measures of change cannot.

Effects of ante-mortem use of methadone on insect succession patterns

Background

Evaluation of insect succession patterns is a scientific method to estimate the time elapsed since death. Several studies have shown that ante-mortem intake of opioids affect maggot growth rate. However, there are few published data that investigate the effect of ante-mortem opioid use on insect succession patterns.

Therefore, the main purpose of this research was to investigate the effect of methadone on the succession patterns of insects on rabbit carcasses during the spring and winter of 2019. In the present study, the H-null hypothesis represents the dissimilarity between the successional waves of species from testing and control carcasses (H0: P: 0).

Results

During this study, 15 and 13 insect species were collected from carcasses during the spring and winter, respectively. The most dominant species during the both seasons were Chrysomya albiceps and Calliphora vicina. These two species preferred to lay eggs on the control carcasses earlier than the treated carcasses. Lucilia cuprina was observed only from the remains of untreated carcasses, while Saprinus chalcites and Necrobia rufipes were recorded only from the remains of treated rabbits. Samples indicate that 11.8% of the insects were members of the Coleoptera. Permutation analyzes based on the Mantel test were 0.647 ± 0.16 (P = 0.009) and 0.693 ± 0.16 (P = 0.003) for the similarity of the species between treated and untreated carcasses in the spring and winter, respectively. Permutation analyzes for the two most dominant fly species (Ch. albiceps and C. vicina) between the treated and untreated carcasses in the spring and winter were 0.515 ± 0.15 (P = 0.05) and 0.491 ± 0.14 (P = 0.09), respectively.

Conclusion

The results revealed that the overall pattern of insect succession was similar between the treated and untreated rabbit carcasses. However, the patterns of succession of Chrysomya albiceps and Calliphora vicina differed slightly between treated and untreated carcasses, and this could have an effect on the PMI min estimate.

Entomological Contributions to the Legal System in Southeastern Spain

The aim of this work is to present a number of forensic cases that took place in Southeastern Spain (Murcia province) in which the entomological evidence aided to fully solve the issues raised during the legal enquiry, enhancing the close interrelationships between experimental studies performed and actual forensic cases assessed. In all cases, the expert report was requested by the police agents or the medical examiners, the latter attempting to make stronger their own conclusions. The assessment of all cases was possible by comparing the evidence and circumstances of each one with the experimental data previously obtained in our laboratory concerning aspects such as faunistic, ecological, morphological, etc., and by considering data from other researchers. In all cases, the evidence could be addressed, although in some cases, it had not been properly collected or processed. Thus, the utility of the experimental studies in forensic practice, even when being considered merely biological, and without immediate practical application, can be demonstrated as well as the need for providing specialized instruction on Forensic Entomology procedures to the different agents involved in forensic investigation.

Temporal variability of the rove beetle (Coleoptera: Staphylinidae) community on small vertebrate carrion and its potential use for forensic entomology

Rove beetles (Coleoptera: Staphylinidae) are one of the most important colonizers of vertebrate cadavers. We have previously investigated carrion-associated rove beetle communities across various forests and demonstrated that the study regions are the main drivers of the local rove beetle species pool that is, in turn, able to colonize a carcass. Nevertheless, little is known about their temporal variation in community composition during the decomposition process. The aim of our study has been to analyze the temporal changes of the composition of the rove beetle community and to identify new, potentially useful candidate species for forensic entomological evaluations. We determined 80 rove beetle species that were attracted to 60 piglet cadavers across various forest stands in Germany. Both the abundance and the community composition changed over the decomposition process, independently of the species-specific geographical variation across study regions. In the region Schorfheide-Chorin, species from the genus Philonthus proved to be a suitable group for future forensic entomological investigations. They appeared in markedly high numbers at piglet cadavers from the bloated stage until the advanced decay stage. For the study region Schwäbische Alb, we newly describe the species Omalium septentrionis as a member of the carrion-associated rove beetle fauna. Based on the geographical variation in rove beetle community compositions, we have filtered out several species that might contribute to advances in postmortem interval estimations or other applied fields in forensic entomological contexts.

Post-Mortem Interval Estimation Based on Insect Evidence: Current Challenges

During death investigations insects are used mostly to estimate the post-mortem interval (PMI). These estimates are only as good as they are close to the true PMI. Therefore, the major challenge for forensic entomology is to reduce the estimation inaccuracy. Here, I review literature in this field to identify research areas that may contribute to the increase in the accuracy of PMI estimation. I conclude that research on the development and succession of carrion insects, thermogenesis in aggregations of their larvae and error rates of the PMI estimation protocols should be prioritized. Challenges of educational and promotional nature are discussed as well, particularly in relation to the collection of insect evidence.

Seasonal Impact of Heroin on Rabbit Carcass Decomposition and Insect Succession

This study investigates the succession of insects and the length of the decomposition of rabbit carcasses injected with heroin. In total, 24 rabbits (2-2.5 kg, Oryctolagus cuniculus domesticus L.) were used in the study. Twelve carcasses were exposed to insect activity in winter (January and February) and 12 in summer (July and August) in Riyadh, Saudi Arabia. Three replicate experiments were conducted in each season. For each experiment, three rabbits were injected with varying doses of heroin, and the fourth rabbit was used as a control, being injected only with saline solution. Insects belonging to the order Diptera, Coleoptera, and Hymenoptera were attracted to the carcasses. In both of the investigated seasons, heroin appeared to delay the decomposition process but did not have a significant impact on the number of insects. In general, the number of flies in both seasons was substantially higher than that of beetles and ants. During the summer, flies were more attracted to treated carcasses with a higher dose of heroin. Some flies such as Musca domestica L. (Diptera: Muscidae) and Chrysomya albiceps Wiedemann (Diptera: Calliphoridae) and some beetles such as Pimelia boyeri Solier (Coleoptera: Tenebrionidae) were represented on the carcasses by different developmental instars (larvae, pupae, and adults). Overall, heroin has not potential effects on the insect succession patterns of insect, however, influences the decomposition of rabbit carcasses. These findings are important while using insects in medicolegal investigation, since heroin is one of the common poisons used as an addictive agent.

Impacts of antemortem ingestion of alcoholic beverages on insect successional patterns

This paper studies the impacts of antemortem ingestion of alcoholic beverages by the domestic rabbit, Oryctolagus cuniculus L., on postmortem successional patterns of insects during winter and summer 2018 in Riyadh, Saudi Arabia. Insect samples were collected from the carcasses of rabbits fed alcoholic beverages as well as untreated rabbits for 15 days postmortem during two successional studies in each season. The results showed that, during both seasons, the decomposition process for the carcasses of rabbits fed alcoholic beverages antemortem was one to two days longer. The results also showed, however, that alcoholic beverages did not affect insect succession patterns in either season. In fact, the number of insects appeared to be influenced by the ambient temperature during the two seasons, with 4415 insects in the winter compared to 1033 insects in the summer. In total, 30 insect taxa were collected during the winter study from the carcasses of rabbits fed alcoholic beverages antemortem; while 26 of these same taxa were collected from the carcasses of the untreated rabbits. Among the treated rabbits, those fed 25 ml alcoholic beverages treated attracted the highest number of insect taxa (24 taxa). In the summer study, 21 insect taxa were collected in total, 19 from the carcasses of the alcohol-treated rabbits and 13 from untreated rabbits. Among the treated rabbits, those fed 50 ml alcoholic beverages attracted the highest number of insect taxa (14 taxa). These results contribute to the understanding of the factors affecting the use of insects in medical investigations, given that alcoholic beverages are a common addictive agent.

Characterization of the Volatiles' Profiles of the Eggs of Forensically Relevant Lucilia sericata and Phormia regina (Diptera: Calliphoridae) Blow Flies by SPME-Facilitated GC-MS

The attraction of necrophagous insects, particularly blow flies, to corpses and carrion is of ecological, economic, and agricultural importance, although the mechanisms by which it occurs are not well understood. Much of the published research on blow fly attractants has focused on volatiles emitted from carrion surrogates, but little attention has been given to the possibility that blow fly eggs themselves may emit chemical cues that are responsible for conspecific and heterospecific insect attraction. In this study, the headspace volatiles emitted from eggs representing two aggregated oviposition events that were collected 1 mo apart from two species of the Calliphoridae family (Order: Diptera), Lucilia sericata (Meigen), and Phormia regina (Meigen) were analyzed via solid-phase microextraction-facilitated GC-MS. The volatiles' profiles were found to be consistent between samples representing the same species, but unique between the two species. Over 100 molecules covering a wide range of compound classes that included alcohols, aldehydes, esters, amines, ketones, and organosulfur compounds were identified. The profile of volatiles emitted from the L. sericata eggs contained several alkanes and aldehydes, whereas salient features of the P. regina headspace included numerous esters and ketones. Between the two species, 42 compounds were shared, several of which were carboxylic acids. Little overlap between the range of compounds detected and those reported to be emitted from decomposing remains was observed.

Relative Insect Frequency and Species Richness on Sun-Exposed and Shaded Rabbit Carrions

On rabbit carcasses (Oryctolagus cuniculus L.) exposed in open and shaded habitats, the relative abundance of insects and species richness were observed. The decomposition process was classified into four stages: fresh, bloated, decayed, and dry. Except for the decayed stage, the elapsed time for each stage of decomposition was similar between open and shaded habitats, with all carcasses reaching dryness in 13 and 14 d, respectively. In total, 2009 insects were collected during the decomposition process with 1,863 flies belonging to seven families and 15 species, and 146 beetles belonging to six species and three families. Insect abundances rose between the fresh and decay stages. The dominant families of insects included Calliphoridae and Muscidae (80.9% of the collected insects) and accounting for 38.07% of the species richness, whereas Histeridae accounted for 4.3% of the collected insects and 14.29% of the species richness. The open habitat attracted 1,233 insects belonging to 18 families, including 1,142 flies and 91 beetles, whereas the shaded habitat attracted 776 insects belonging to 18 families, including 721 flies and 55 beetles. Diversity level and ratios of exclusive species are also reported for each habitat (open 61.4%; shaded 38.6%). Between habitats, there were substantially separate insect communities, however. In addition, there was a substantial difference in the insect number and species between decomposition stages. This study demonstrates that the exposure status needs to be evaluated and examined when estimating the time since death.

Development of Necrobia rufipes (De Geer, 1775) (Coleoptera: Cleridae) under constant temperatures and its implication in forensic entomology

After the death of humans or animals, the odors released at different stages of decay attract various insects, and other arthropods, to the corpses. Therefore, the development of insects, and other arthropods present on corpses, can be assessed to estimate the minimum postmortem interval since death. In general, necrophagous blow flies are the insects that first colonize corpses. With progressing decay, other necrophagous and predatory insects arrive at the corpses, which will develop on or around these either by feeding directly on the corpses or by prey on other immature insects. Beetles (Coleoptera) mainly arrive at the corpses during the later stages of decay, and play important roles in cases with longer postmortem intervals. Necrobia rufipes (De Geer, 1755) (Coleoptera: Cleridae) is an important stored-product species with world-wide distribution. Moreover, it is also a forensically important insect species. At temperatures of 22, 25, 28, 31, 34, and 36°C (±0.5°C), the developmental periods from egg to adult were 113.20±2.96, 66.16±3.22, 50.61±1.95, 38.26±2.48, 37.97±2.40, and 31.20±2.11 days, respectively. In vivo measurements obtained the morphological indexes of larvae. The growth curve and the equation of the relationship between development time, body lengths, and mesonotum widths were simulated. The isomorphen diagram model, the isomegalen diagram model, and the thermal summation model were established. In addition, the widths of head capsules and pronota of larvae at different instars were determined by cluster analysis. Classifiers were created and validated by linear discriminant analysis.

Succession study on forensically important Coleoptera from India: a preliminary study and its forensic implications

Background

Coleoptera is the second most important group of entomofauna associated with decomposition, yet little is known about its role in decomposition and postmortem colonization of carcasses in India and other parts of the world. Consequently, a preliminary study was conducted to study the succession of forensically important Coleoptera using goat carrion as an animal model.

Results

Five decomposition stages were observed during the experiment. A total of 1174 adult coleopterans belonging to 21 species and seven families were collected during this study. Throughout faunal succession, Histeridae and Silphidae were the dominant Coleopteran families, and they occurred mainly during the bloated and decay stages of decomposition; Necrophila (Calosilpha) ioptera was the dominant species present from the bloated to dry stage of putrescence. Two species, Pachylister bellicus and Saprinus sternifossa were reported for the first time from India.

Conclusion

This study provides baseline data regarding Coleopteran species associated with different decomposition stages, but more extensive studies need to be performed to develop a geographical database on arthropod succession from as many habitats as possible so that this kind of data can be used in forensic cases.

Succession of oral microbiota community as a tool to estimate postmortem interval

The establishment of postmortem interval is one of the most important aspects of forensic expertise. Microbes may provide a novel way to estimate the postmortem intervals in order to avoid many of these limitations. The oral cavity harbors one of the most diverse microbiomes that play a key role in the decomposition of corpses. In this study, the oral bacterial community showed obvious changes in relative abundance during the process of mice decomposition. Meanwhile, at different taxonomic levels, specific bacteria were found to be significantly correlated with the postmortem interval. Linear regression models between relative abundance and the postmortem interval were constructed. Among these species, Gamma-proteobacteria and Proteus were the best ones that can be used to infer the postmortem interval, especially late postmortem interval. Therefore, we suggest that succession of oral microbial community can be developed as a forensic tool for estimating the postmortem interval.

Long-term insect successional patterns on pig carcasses in central Spain

Baseline data on the insect successional patterns on carcasses can be a valuable estimation tool in the investigations of suspicious deaths, particularly when the post-mortem interval is longer than months or years. However, although carrion insect succession is a recurrent topic in forensic science research, the duration of the published studies is typically shorter than 1 year, with only one published study from central Europe documenting successional patterns beyond the first year of decomposition. We provide here the first data on the long-term insect successional patterns in southern Europe, using pig carcasses exposed in the four seasons of the year and documenting the carrion entomofauna during the second and third year of decomposition. Our results confirmed previous observations from central Europe that several Coleoptera species are able to recolonize cadavers during the second and third year after death, with their larvae residing on the remains for long periods. The season of cadaver exposure appears to be a main factor determining the composition of the insect fauna that exploits the remains during subsequent years. Our results suggest that it might be possible to estimate the year and season of death analyzing the composition of the insect fauna occurring on a cadaver. The present data highlight the need for further studies on the long-term insect succession on cadavers in different seasons and geographical areas, in order to fully understand its patterns and ensure its proper application in PMI estimations.

Larval identification key to necrophagous Coleoptera of medico-legal importance in the western Palaearctic

Several necrophagous Coleoptera species are frequently collected on cadavers, may occasionally act as intermediate or paratenic hosts of parasites, as vectors of pathogens or as allergens, and can also represent major pests of preserved animal products. However, despite their medical, veterinary and economic importance, there is a lack of reliable species identification tools for the larval stages (usually the only entomological evidence associated with medicolegal investigations), thus severely limiting their potential application as forensic indicators. Here, we provide an identification key to the larvae of the necrophagous Coleoptera species which have been recorded on carrion in the western Palaearctic region, based on easily observable morphological characters. In total, we provide diagnostic characters for the reliable identification of 23 necrophagous Coleoptera species within four different families (Cleridae, Dermestidae, Nitidulidae and Silphidae). In addition to the aforementioned families, we provide diagnostic characters for the identification of the larvae of families Histeridae, Staphylinidae and Trogidae, which can also be collected on cadavers. It is expected that the present key will facilitate the identification of larval material of necrophagous Coleoptera collected either in carrion succession studies or during medicolegal investigations, in order to further advance in the potential use of this insects as forensic tools.

Annual variation in decomposition and insect succession at a periurban area of central Iberian Peninsula

The variation in decomposition and insect succession among the four seasons of one year was studied for the first time in a periurban area of central Spain. During the winter trial, the carcasses showed corification, a cadaveric preservation phenomenon which apparently leaded to a significant delay in decomposition processes. The composition of the insect fauna breeding on carcasses changed significantly between trials. Active decay was mainly driven by Calliphoridae (Diptera) larvae in every season except in winter trial, when larvae of Thanatophilus species (Coleoptera: Silphidae) were the main consumers of soft tissues. Advanced decay was characterized by the occurrence of Dermestidae, Silphidae, Cleridae, Nitidulidae (Coleoptera) and Piophilidae (Diptera) larvae. Differences in the species composition in comparison with other regions of the Iberian Peninsula were also observed. The current paper provides baseline and preliminary information on the insect succession on carrion in central Spain, as well as a starting point for further research on forensic entomology in this region.

Diversity of the Formicidae (Hymenoptera) carrion communities in Lisbon (Portugal): preliminary approach as seasonal and geographic indicators

The value of the Formicidae (Insecta, Hymenoptera) community in forensic investigations is poorly studied in Portugal. In order to better understand the structure and dynamics of this group of insects in cadavers and their putative value in forensic investigations, studies were carried out in Lisbon area during one year. Piglet carcasses were used as a model of human decomposition. The entomofauna attracted to the carcasses was collected over a period of about 2 months in each season of the year. The collection of ants was performed at regular intervals, daily in the first 23 days and then with intervals of 2, 3 or 5 days until the end of the experiment. Five stages of cadaveric decomposition were recognized with the ants being present in all of them. Three hundred and nine specimens were captured: 7 in autumn, 6 in winter, 90 in spring and 206 in summer. These specimens belong to three subfamilies and seven different species. Four of them had never been mentioned before as being associated to cadavers in this geographical area. Spring and summer had the greater diversity of species and a larger number of individuals. Temnothorax luteus was the dominant species in spring and Tapinoma nigerrimum in summer. Corroborating the information of other similar studies carried out in the Iberian Peninsula, the sarcosaprophagous Formicidae community found in Lisbon is unique and different from other studied locations, which supports the need to perform regional studies. Our results shown that ants do not present a definite pattern of succession, but some species have the potential to be seasonal or geographic indicators.

Effect of Temperature on the Survival and Development of Three Forensically Relevant Dermestes Species (Coleoptera: Dermestidae)

Most Dermestes species (Coleoptera: Dermestidae) are scavengers during both larval and adult stages, with a preference for dry organic matter. Because of this, Dermestes beetles are potentially useful indicators in forensic investigations concerning skeletonized and mummified human remains. However, there is a paucity of reference developmental data on most forensically relevant Dermestes species. This study analyses the effect of five constant temperatures (15, 20, 25, 30, and 35 °C) on the survival and developmental rates of three of the forensically most relevant dermestids: Dermestes frischii Kugelan, Dermestes maculatus De Geer, and Dermestes undulatus Brahm. Pig skin was used as rearing substrate, to use a substrate as similar as possible to that exploited in nature. Overall, the temperature had a significant effect on the survival and the duration of development, with optimal values at intermediate temperatures. Both D. frischii and D. maculatus showed similar developmental rates and the shortest developmental times at 30 °C, whereas D. undulatus developed faster at lower temperatures. At 15 °C, both D. frischii and D. undulatus did not oviposit, whereas no D. maculatus individuals survived beyond the pupal stage. An inconsistent number of larval instars per individual were observed across different constant temperatures in the three species. The present study aims to provide baseline developmental data for further advances in the potential use of Dermestes beetles as forensic tools in long postmortem interval cases.

Sex- and Size-Related Patterns of Carrion Visitation in Necrodes littoralis (Coleoptera: Silphidae) and Creophilus maxillosus (Coleoptera: Staphylinidae)

The estimation of postmortem interval (PMI) based on successional patterns of adult insects is largely limited, due to the lack of potential PMI markers. Sex and size of adult insects could be easily used for such estimation. In this study, sex- and size-related patterns of carrion attendance by adult insects were analyzed in Necrodes littoralis (Coleoptera: Silphidae) and Creophilus maxillosus (Coleoptera: Staphylinidae). For both species, abundance of males and females changed similarly during decomposition. A slightly female-biased sex ratio was recorded in N. littoralis. Females of N. littoralis started visiting carcasses, on average, one day earlier than males. There was a rise in size of males of N. littoralis at the end of decomposition, whereas for females of both species and males of C. maxillosus, no size-related patterns of carrion visitation were found. Current results demonstrate that size and sex of adult carrion beetles are poor indicators of PMI.

Carrion beetles succession in three different habitats in Riyadh, Saudi Arabia

A main objective of the study is the establishment of a forensic entomological database for Riyadh, Saudi Arabia. Decomposition processes and beetle succession were analysed on rabbit carcasses in three different habitats (agricultural, desert and urban) in the period from May to July 2014. Due to the effects of the high temperature at the study sites, carrion reached the dry stage within 12 days in the agricultural habitat, and 6 days in the desert and urban habitats. A total of 125 beetles belonging to eight species and five families were collected during the decaying process, with their abundances increasing from the fresh to decay stages. The prevailing species belonged to the families of Dermestidae and Histeridae. It was not possible to confirm any definitive relationship between the occurrence of a single species and a particular stage of decomposition. The beetle communities were also not distinctively different between desert and urban habitats, but a distinct community was evident in the agriculture habitat. In addition, there were distinct beetle communities between the decay stage and the other stages. The dry stage recorded the lowest number of beetles. This study indicated that, the habitat type had an effect on the decay process and the abundance rate of the beetles.

From water to land: How an invasive clam may function as a resource pulse to terrestrial invertebrates

Resource pulses are episodes of low frequency, large magnitude and short duration that result in increased resource availability in space and time, with consequences for food web dynamics. Studies assessing the importance of resource pulses by invasive alien species in the interface between terrestrial and aquatic ecosystems are rare, especially those in the direction from water to land. This study assessed the importance of massive die-offs of the Asian clam Corbicula fluminea (Müller, 1774) as a resource pulse to the terrestrial invertebrate community after an extreme climatic event using a manipulative experiment. We used 5 levels of C. fluminea density (0, 100, 500, 1000 and 2000ind·m(-2)), with terrestrial invertebrates being censused 7, 30 and 90days after C. fluminea addition. We also assessed the possible effect of plots position, where plots that delimited the experiment were assigned as edge plots and the remaining as core plots. Clear differences were detected in abundance, biomass, richness and diversity of terrestrial invertebrates depending on the C. fluminea density, time and position. Interestingly, the highest abundance of adult Diptera was observed 7days after C. fluminea addition, whereas that of the other terrestrial invertebrates was on day 30, both with C. fluminea densities higher than 500ind·m(-2) located on the edge of the experimental design. This study highlights the importance of major resource pulses after massive die-offs of invasive bivalves, contributing with remarkable amounts of carrion for adjacent terrestrial systems. Part of this carrion can be consumed directly by a great number of invertebrate species while the remainder can enter the detrital food web. Given the high density and biomass attained by several invasive bivalves worldwide and the predicted increase in the number, intensity and magnitude of extreme climatic events, the ecological importance of this phenomenon should be further investigated.

The biology and ecology of Necrodes littoralis, a species of forensic interest in Europe

Necrodes littoralis (Linnaeus, 1758) (Coleoptera: Silphidae), also known as the "shore sexton beetle," is a common silphid beetle that visits and breeds on large vertebrate cadavers. This study describes, for the first time, the involvement of N. littoralis on human corpses based on a large dataset of 154 French forensic cases. Various parameters regarding corpse location, decomposition stages, and entomofauna were extracted from each file. Compared to all of the forensic entomology cases analyzed between 1990 and 2013 (1028), N. littoralis was observed, on average, in one case out of eight; most of these cases occurred during spring and summer (73.5%). More than 90% of the cases were located outdoors, especially in woodlands, bushes, and fields. The decomposition stage of the corpse varied among cases, with more than 50% in the advanced decomposition stage, 36% in the early decomposition stage, and less than 10% in the fresh, mummified, or skeletonized stages. Regarding other necrophagous species sampled with N. littoralis, Calliphorid flies were found in 94% of the cases and Fanniidae/Muscidae in 65% of the cases. Chrysomya albiceps, a heliophilic species mostly located in the Mediterranean area, was present in 34% of the cases (only 20% in the whole dataset). The most common coleopteran species were Necrobia spp. (Coleoptera: Cleridae) and Creophilus maxillosus (Coleoptera: Staphylinidae); these beetles were observed in 27% of the cases. The over-representation of these species is likely due to similar requirements regarding the climate and decomposition stage. As N. littoralis is frequently observed and tends to become more common, we conclude that the developmental data for this species would be a precious tool for forensic entomologists in Europe.

Necrophilous Histerid Beetle Communities (Coleoptera: Histeridae) in Central Spain: Species Composition and Habitat Preferences

Despite the applied importance of necrophilous histerid beetles, their communities and habitat preferences had not been characterized in the Iberian Peninsula. The current article describes the composition of those communities in seven types of natural habitats along a bioclimatical gradient in central Spain, describing and discussing the habitat preferences and niche breadths of the most abundant species. In total, 25 species of necrophilous Histeridae were collected using carrion-baited traps. As a result, six groups of species can be distinguished according to their habitat preferences. These groupings depend on either the distribution among habitats or their restriction to certain habitats. Moreover, within each habitat, the type of vegetation was a factor structuring histerid communities, with those species with wide distribution throughout several habitats showing a preference for more open areas.

Effect of body mass and clothing on carrion entomofauna

Carcass mass largely affects pattern and rate of carrion decomposition. Supposedly, it is similarly important for carrion entomofauna; however, most of its likely effects have not been tested experimentally. Here, simultaneous effects of carcass mass and clothing are analyzed. A factorial block experiment with four levels of carcass mass (small carcasses 5–15 kg, medium carcasses 15.1–30 kg, medium/large carcasses 35–50 kg, large carcasses 55–70 kg) and two levels of carcass clothing (clothed and unclothed) was made in a grassland habitat of Western Poland. Pig carcasses (N = 24) were grouped into spring, early summer, and late summer blocks. Insects were sampled manually and with pitfall traps. Results demonstrate that insect assemblages are more complex, abundant, and long-lasting on larger carcasses, whereas clothing is of minor importance in this respect. Only large or medium/large carcasses were colonized by all guilds of carrion insects, while small or medium carcasses revealed high underrepresentation of late-colonizing insects (e.g., Cleridae or Nitidulidae). This finding indicates that carcasses weighing about 23 kg—a standard in forensic decomposition studies—give an incomplete picture of carrion entomofauna. Residencies of all forensically relevant insects were distinctly prolonged on larger carcasses, indicating that cadaver mass is a factor of great importance in this respect. The pre-appearance interval of most taxa was found to be unrelated to mass or clothing of a carcass. Moreover, current results suggest that rate of larval development is higher on smaller carcasses. In conclusion, this study demonstrates that carcass mass is a factor of crucial importance for carrion entomofauna, whereas the importance of clothing is small.

Factors affecting quality of temperature models for the pre-appearance interval of forensically useful insects

In the case of many forensically important insects an interval preceding appearance of an insect stage on a corpse (called the pre-appearance interval or PAI) is strongly temperature-dependent. Accordingly, it was proposed to estimate PAI from temperature by using temperature models for PAI of particular insect species and temperature data specific for a given case. The quality of temperature models for PAI depends on the protocols for PAI field studies. In this article we analyze effects of sampling frequency and techniques, temperature data, as well as the size of a sample on the quality of PAI models. Models were created by using data from a largely replicated PAI field study, and their performance in estimation was tested with external body of PAI data. It was found that low frequency of insect sampling distinctly deteriorated temperature models for PAI. The effect of sampling techniques was clearly smaller. Temperature data from local weather station gave models of poor quality, however their retrospective correction clearly improved the models. Most importantly, current results demonstrate that sample size in PAI field studies may be substantially reduced, with no model deterioration. Samples consisting of 11-14 carcasses gave models of high quality, as long as the whole range of relevant temperatures was studied. Moreover, it was found that carcasses exposed in forests and carcasses exposed in early spring are particularly important, as they ensure that PAI data is collected at low temperatures. A preliminary best practice model for PAI field studies is given.

Comparison of the decomposition VOC profile during winter and summer in a moist, mid-latitude (Cfb) climate

The investigation of volatile organic compounds (VOCs) associated with decomposition is an emerging field in forensic taphonomy due to their importance in locating human remains using biological detectors such as insects and canines. A consistent decomposition VOC profile has not yet been elucidated due to the intrinsic impact of the environment on the decomposition process in different climatic zones. The study of decomposition VOCs has typically occurred during the warmer months to enable chemical profiling of all decomposition stages. The present study investigated the decomposition VOC profile in air during both warmer and cooler months in a moist, mid-latitude (Cfb) climate as decomposition occurs year-round in this environment. Pig carcasses (Sus scrofa domesticus L.) were placed on a soil surface to decompose naturally and their VOC profile was monitored during the winter and summer months. Corresponding control sites were also monitored to determine the natural VOC profile of the surrounding soil and vegetation. VOC samples were collected onto sorbent tubes and analyzed using comprehensive two-dimensional gas chromatography – time-of-flight mass spectrometry (GC×GC-TOFMS). The summer months were characterized by higher temperatures and solar radiation, greater rainfall accumulation, and comparable humidity when compared to the winter months. The rate of decomposition was faster and the number and abundance of VOCs was proportionally higher in summer. However, a similar trend was observed in winter and summer demonstrating a rapid increase in VOC abundance during active decay with a second increase in abundance occurring later in the decomposition process. Sulfur-containing compounds, alcohols and ketones represented the most abundant classes of compounds in both seasons, although almost all 10 compound classes identified contributed to discriminating the stages of decomposition throughout both seasons. The advantages of GC×GC-TOFMS were demonstrated for detecting and identifying trace levels of VOCs, particularly ethers, which are rarely reported as decomposition VOCs.

Necrophilous Staphylininae (Coleoptera: Staphylinidae) as indicators of season of death and corpse relocation

Several case studies confirm that habitat and seasonal preferences of necrophilous insects are the source of valuable information about the season of death or corpse relocation. Rove beetles (Staphylinidae) are common predators found on corpses and subfamily Staphylininae includes species of the largest forensic importance. In order to evaluate usefulness of Staphylininae as indicators of season of death or corpse relocation, a pig carrion experiment was made from April to October in open and forest habitats of Central Europe. Forty species of Staphylininae were collected, with hairy rove beetle (Creophilus maxillosus) being the most abundant. Some species exhibited a clear preference towards particular habitats. It was found that Philonthus lepidus was exclusive to open habitats and therefore may be useful as indicator of corpse relocation from open to forest habitats. Philonthus decorus was the only species found exclusively on carcasses in forests. Clear seasonality was present in nine species. Philonthus lepidus, Bisnius nitidulus, Philonthusconcinnus and Gabrius osseticus were spring-early summer species, while Philonthusspinipes and Ocypus olens were late summer-early fall species. Bisnius fimetarius and Staphylinus erythropterus were spring-summer species. Platydracus stercorarius was summer species. These results indicate that some Staphylininae are good candidates for indicators of season of death or corpse relocation.

Instar determination in forensically useful beetles Necrodes littoralis (Silphidae) and Creophilus maxillosus (Staphylinidae)

In order to estimate postmortem interval from immature insects, it is necessary to accurately determine which instars are present in a corpse sample. Unfortunately, most forensically useful beetles lack morphological features specific for particular instars, and the only way to distinguish larval instars of particular species is to measure their size. The aim of this study was to test which measurements are useful for instar determination of Necrodes littoralis (Silphidae) and Creophilus maxillosus (Staphylinidae) and how to combine them to get accurate and easy to use instar classifier. Six morphological features were measured: distance between dorsal stemmata, width of the pronotum, length of the body, width of the mesonotum, width of the eighth abdominal tergite and length of the first segment of urogomphus. Linear discriminant analysis (LDA) was used to create and validate classifiers. Validation was made with fully sclerotized larvae and larvae just after ecdysis (not fully sclerotized and coloured). All the features were found to be useful for instar determination. The most useful features were the width of the mesonotum and the distance between dorsal stemmata. Complete classifiers (the ones incorporating all features) assigned larvae to instars with no misclassifications, unless larval specimens were just after ecdysis. Even in the case of larvae just after ecdysis complete classifiers were highly effective, although some third instars of C. maxillosus were misclassified as second instars. Simple classifiers (the ones incorporating only two, the best features) performed similarly well with fully sclerotized larvae, but in the case of larvae just after ecdysis they revealed higher misclassification rate than complete classifiers. These results indicate that measurement of any highly sclerotized larval structure of N. littoralis and C. maxillosus may be useful for instar determination. They also show that fully sclerotized larvae may be accurately classified according to instar from just two measurements, whereas larvae just after ecdysis will require more measurements.