A roadmap for bridging basic and applied research in forensic entomology

Dipteran succession on decomposing domestic pig carcasses in a rural area of southeastern Brazil

Diptera plays a pivotal role in forensic investigations, particularly in estimating the post-mortem interval. This can be achieved by analyzing the succession patterns of species on decomposing bodies, which requires detailed knowledge of the local fauna. In rural areas of the Rio de Janeiro state, Brazil, forensic entomological succession remains understudied. This study aimed to evaluate the ecological succession of adult and immature dipterans on decomposing pig carcasses in rural areas of Seropédica municipality during dry and rainy seasons, through the threshold indicator taxa analysis (TITAN). For adult dipterans during the rainy season, we identified 25 'Z-' taxa, with change points (cp) between days 4 and 14, while one 'Z+' taxon showed a cp at day 16. During the dry season, 22 'Z-' taxa exhibited cp between days 4 and 1, and one 'Z+' taxon was identified on day 13. Among immature dipterans, we identified 3 'Z-' taxa with cp between days 9 and 16, while 2 'Z+' taxa showed cp. at days 5 and 21.5. Our findings provide valuable insights for forensic professionals by offering continuous ecological change point analysis, which help address the challenges of interpreting heterogeneous decomposition stages, which are often difficult to delineate in forensic casework.

Species Richness and Distribution of Calliphoridae Along an Elevation Gradient in Sicily (Italy) and Ecuador

Blow flies (Diptera: Calliphoridae) are among the first insects to arrive on a corpse, and so they are particularly important in forensic entomology. To use blow flies in forensic investigations, there must be information available on their species diversity, abundance, and distribution in the areas where investigations are conducted. Several factors can contribute to species distribution, and elevation is one of those factors. The purpose of this study was to document the distribution of Calliphoridae across four elevational gradients in Sicily and Ecuador, where little information is available. Baited traps were placed at elevations ranging from 20 m to 1552 m in Sicily (a major island and region of Italy and a distinct ecoregion) and 561 m to 3336 m in Ecuador. Species richness, relative abundance, and diversity were calculated, as well as the ratio of female to male blow flies and community assemblage. Twelve species were collected in Sicily, and seventeen species were collected in Ecuador. In Sicily, the most abundant species was Lucilia sericata (Meigen) (68.50% of the total capture), while in Ecuador, it was Compsomyiops verena (Walker) (51.67% of the total capture). In Sicily, significant differences were only observed in the relative abundance of L. sericata across elevations. In Ecuador, significant differences were observed in the relative abundance of Calliphora nigribasis (Macquart), Chrysomya albiceps (Wiedemann), C. verena, Hemilucilia semidiaphana (Rondani), Lucilia ibis (Shannon), L. purpurascens (Walker), and Paralucilia sp. across elevations. These data can help build a checklist of blow fly species in these two regions and can be instrumental in environmental and forensic investigations.

Estimating the Intra-Puparial Period of Chrysomya nigripes Aubertin Using Morphology and Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) Spectroscopy

Chrysomya nigripes Aubertin, 1932, is a species of Calliphoridae widely distributed in Southeast Asia, with studies and case reports confirming the value of this species in estimating the minimum postmortem interval (PMImin). However, data on the growth and development of this species' intra-puparial age are not yet complete. Here, we investigated the intra-puparial morphological changes of C. nigripes at seven temperatures, ranging from 16 °C to 34 °C. We also investigated the potential value of Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) coupled with chemometric methods for the intra-puparial age estimation of C. nigripes at 19 °C, 25 °C, and 31 °C. The spectral data within the wavenumber range of 1800-900 cm-1, collected from the second thoracic segment of all puparia, were processed. Through this procedure, the mean values of ATR-FTIR spectra of C. nigripes of puparia at each intra-puparial age under various constant temperature conditions were obtained. The results showed that at 16 °C, C. nigripes could not complete its developmental process, while it could do so at the remaining six constant temperatures. With an increase in temperature, the average duration of the intra-puparial period was reduced from the longest at 19 °C of 192 ± 0 h to 77.3 ± 4.6 h at 34 °C. The intra-puparial morphological changes were divided into 12 sub-stages, and the development of the compound eyes, mouthparts, antennae, thorax, legs, wings, and abdomen were divided into 6-8 sub-stages. The Partial Least Squares Discriminant Analysis (PLS-DA) classification model predicted better results compared to the Random Forest (RF) classification model, with an accuracy of 58.3%, 77.8%, and 100% at 19 °C, 25 °C, and 31 °C, respectively. In this study, each sub-stage of the C. nigripes pupa and the time range of structure emergence were recorded, and it was concluded that the spectral trends were time-dependent. Thus, ATR-FTIR combined with chemometrics could also be used as a tool to assist in estimating the intra-puparial stage of C. nigripes and provide a reference value for PMImin.

Population and sexual fluctuation of Calliphoridae and Mesembrinellidae (Diptera: Oestroidea) in the Atlantic forest of Rio de Janeiro

Dipterans of the Calliphoridae and Mesembrinellidae families are of high relevance in the Atlantic Forest of Rio de Janeiro, and it is important to examine their diversity and abundance in the different ecological areas of this biome over a time interval. This study aimed to study the diversity and abundance of Calliphoridae and Mesembrinellidae by evaluating the sexual variation and the influence of abiotic factors (average temperature, relative humidity and total precipitation) on the capture of insects collected during the four seasons of the year. Four traps were installed in each ecological area containing 300 grams of beef liver as attractive bait, which remained exposed for 48 hours in each season during the period between autumn 2021 and summer 2022. The collected dipterans were sacrificed, sent to the Laboratório de Estudos de Dípteros (LED-UNIRIO), and taxonomically identified. The Kruskal-Wallis and Wilcoxon tests were used to examine the influence of the four seasons on the abundance, and the Spearman correlation was used to relate abundance to abiotic variables. A total of 2,826 dipterans were collected during the four seasons of the year, represented by nine species of the Calliphoridae family and ten of the Mesembrinellidae family. During the summer, a numerically larger amount of insects was collected, but the Kruskal-Wallis test (chi-square = 5.2781, p = 0.1525) showed there was no significant difference between the abundance of the species collected and the seasons. Spearman's correlation showed that most species did not show a significant correlation between their respective abundances and the analyzed abiotic factors. The Wilcoxon test indicated that there is a significant difference between the abundance of females and males, with females being significantly more abundant than males, however the difference is statistically greater within the Calliphoridae family (W = 60.49, p = 5.8x10-12) in relation to the Mesembrinellidae family (W = 1231.5, p = 0.019).

Development of a Baltimore (MD) population of Calliphora vicina (Diptera: Calliphoridae) reared at several temperatures and estimations of developmental limits and thresholds

Developmental data for necrophagous Diptera are frequently used in medico-legal investigations to estimate portions of the postmortem interval and interpret periods of insect activity. These applications require baseline developmental data for local populations from geographic locations of interest. For the widely distributed blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae), detailed developmental data does not exist for many locations in the mid-Atlantic region of the United States. This study examined development of C. vicina collected from a large, metropolitan city (Baltimore) in Maryland utilizing 11 ambient temperatures. The developmental threshold and thermal range of growth and tolerance were also estimated, as well as critical thermal minima and maxima based on thermal injury. For this population, linear growth was observed between 10°C and 25°C, whereas flies failed to complete development at temperatures below 7°C or above 28°C. Growth at low temperatures was not curvilinear, which contrasts with other developmental studies using C. vicina and other calliphorids. The lower developmental threshold was estimated to be 5.9°C and corresponds closely with experimental observations. The implications of these result in reference to phenotypic plasticity in populations of C. vicina and applications in forensic entomology are discussed.

Variation in the community composition of blow flies (Diptera: Calliphoridae) in neighboring deserts within Joshua Tree National Park

Joshua Tree National Park (JOTR) in southern California offers a unique opportunity to explore insect biodiversity across 2 distinct desert ecosystems: the lower-elevation Sonoran Desert and the higher-elevation Mojave Desert. In these harsh environments, many blow flies (Diptera: Calliphoridae) serve as important decomposers, feeding on animal waste and decomposing tissue. Some blow fly species, notably non-native species, are associated with human activity, which underscores the need to study their communities in JOTR, where annual visitation has reached 3 million. This study investigated the community composition of blow flies across the park and assessed the impact of visitor activity on blow fly communities in JOTR. Sampling from 2021 to 2023 using traps baited with squid carcasses revealed higher blow fly diversity in the Mojave Desert relative to the Sonoran Desert, in contrast to previous insect and vegetation surveys within the park. Across the park, blow fly community composition (i.e., β-diversity) differed by season. Blow fly abundance, richness, and diversity were similar between low- and high-visitor activity sites. However, more non-native species were collected in areas of low visitor activity, suggesting regular waste removal practices in high-visitation sites might limit their ability to complete development as secondary colonizers. This study is the first to characterize blow fly communities in Joshua Tree National Park. These findings demonstrate that blow fly communities reflect previously established park boundaries and underscore the importance of waste management practices in reducing the spread of non-native species throughout the park.

Effect of fluctuating temperatures on the development of forensically important fly species, Chrysomya megacephala (Diptera: Calliphoridae)

Necrophagous blow flies are a commonly used forensic tool to estimate the minimum postmortem interval (PMImin), where researchers collect development data under constant temperature regimes and construct models to estimate PMImin. However, the ambient temperatures of real death scenes are often fluctuant, which limits the reliability of data obtained under constant temperature regimes. Here we investigate the possible differences in the development of Chrysomya megacephala (Fabricius, 1794) (Diptera: Calliphoridae), an important species in forensic entomology. Chrysomya megacephala was exposed to nine temperature regimes with both large and small fluctuations, including a 19℃ constant temperature (19CT), 19℃ average with fluctuating temperatures 1 (19FT1) (16-22℃), a 19℃ average with fluctuating temperatures 2 (19FT2) (12-30℃), as well as 25CT (25℃), 25FT1 (22-28℃), 25FT2 (16-34℃), 28CT (28℃), 28FT1 (25-31℃) and 28FT2 (18-38℃). The total developmental durations of C. megacephala were 463.94 h (19CT), 534.50 h (19FT1), 507.78 h (19FT2), 273.70 h (25CT), 293.80 h (25FT1), 302.89 h (25FT2), 230.00 h (28CT), 245.84 h (28FT1) and 265.17 h (28FT2), respectively. The results showed that the developmental time of C. megacephala under fluctuating temperatures was longer than at constant temperatures. Except for 19℃, large amplitude fluctuating temperatures resulted in more developmental delays. Although there were numerical differences in the developmental time of almost all the stages of C. megacephala at fluctuating temperatures compared with constant temperatures, the Kruskal-Wallis test only found statistically significant differences during a few developmental stages (p < 0.05). We also used the larval body length equations constructed with constant temperature data to verify larval growth at fluctuating temperatures and found that there was a deviation between the estimated development time and the actual development time. These results are reference for the application and correction of C. megacephala data, aiding in the accurate estimation of PMImin.

Retrospective review of forensic entomology casework in eastern Australia from 1994 to 2022

Forensic entomology can be a crucial source of information for medicolegal investigations, with its most well-known application being for estimating minimum post-mortem interval (mPMI) in death investigations. The analysis of entomological evidence requires robust data on insect ecology, life history, behaviour, and taxonomy. In Australia, substantial basic research on forensically relevant insects has focused predominately in the populous southeast and southwest; however, knowledge gaps remain, most importantly for the tropical north. In addition, there are scant casework data available publicly, which limits the ability of practitioners to make connections between fundamental research and real-world casework and hampers refinement of analytical methods and techniques. To address this gap, this project collated and analysed data from expert forensic entomological casework reports for five eastern Australia jurisdictions (South Australia, Victoria, New South Wales, Australian Capital Territory and Queensland) for a period spanning nearly thirty years (1994-2022). Relevant data extracted from casework reports included species and life stages collected, various decedent and case characteristics, type of opinion requested and estimated mPMI. These data were used to explore associations between species composition and geographical region, surrounding environment, season, and decedent characteristics (e.g., wounds). Additionally, the accuracy and investigative 'value' of mPMI estimates was assessed, which demonstrated that entomology-derived timeframes are largely reliable and highly informative. Finally, we report the first records in Australian casework for several species and highlight several areas that require additional research to fill critical gaps in our knowledge. Overall, this review represents highly practical real-world data that will be of enduring benefit to the forensic community.

Challenges and considerations in forensic entomology: A comprehensive review

Forensic entomology is the study of insect biology as it relates to societal problems that come to the attention of the legal profession and that often must be resolved by legal proceedings. These problems come under the purview of medico-criminal entomology. Forensic entomology is the study of arthropods, especially insects, their identification, post-mortem intervals (PMI), crime scene details associated with crimes and other aspects of the courts and judicial system. Understanding the predictable succession patterns of Diptera and Coleoptera on decomposing remains is crucial for accurately determining the post-mortem interval in forensic investigations. Beetles and blowflies play a critical role in the decomposition process, with beetles often appearing later and blowflies swiftly colonizing remains, making both essential for accurately estimating the post-mortem interval and understanding decomposition dynamics. Insects, particularly flies, serve as crucial forensic tools, allowing for detecting drugs, poisons, and other substances long after traditional tissue samples degrade. Their ability to retain and reveal evidence, even in severely decomposed or altered remains, significantly enhances the accuracy of criminal investigations. Recent advancements in forensic entomology, such as integrating infrared spectroscopy, omics technologies, and molecular taxonomy, have significantly improved the precision and scope of forensic investigations. These tools, combined with thorough validation processes, enable forensic scientists to identify species, estimate post-mortem intervals, and interpret complex cases with greater accuracy and reliability. However, challenges such as environmental influences, insect behavior, body concealment, faunal succession limitations, and gaps in knowledge and resources present obstacles to accuracy and standardization. This review summarises key insect species involved in crime Investigation, PMI Intervals and their significance, Recent advances, Challenges and limitations so that entomotoxicologists can analyze challenging cases recovered after a long period this review also analyses the scope of entomotoxicology in the area of death investigations.

Exploring the impact of xenobiotic drugs on forensic entomology for accurate post-mortem interval estimation

Forensic entomotoxicology is an emerging field within forensic entomology that investigates the effects of chemicals, drugs, and toxins on insect development and their implications for postmortem interval (PMI) estimation. This systematic overview delves into the influence of drugs such as Morphine, heroin, Opiates, and cocaine on the variables affecting the use of forensically significant insects as evidence tools. Notably, it has been observed that the presence of drugs does not appear to alter the progression of the lifecycle from the first instar to the emergence of flies, indicating that PMI estimations based on fly emergence remain unaffected by drugs. However, larvae treated with drugs frequently show delayed pupation, suggesting the need for further research into the impact of different compounds on various insect species over more extended observation periods. Additionally, conflicting results have been noted regarding how toxins can influence the developmental process in larvae, underscoring the necessity to assess the effect of different classes of compounds on other insect species. The study also recommends exploring factors such as the samples' collection site and the drugs' pathological implications to inspire future research. Furthermore, the paper underscores the potential for varying drug effects across insect species, emphasizing the complexity of interpreting drug impacts on PMI estimations. This systematic review was conducted by the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) guidelines.

A review of the estimation of postmortem interval using forensic entomology

The postmortem interval (PMI) is a crucial factor in death investigations. For PMIs exceeding 24 h the forensic pathologist must turn to other specialties that focus on decompositional ecology of animals, including humans. Primary among these specialties is forensic entomology. Here, we review the importance of forensic entomology in estimating the PMI, and we examine the factors that influence these estimates. Among key concerns are environmental factors, especially temperature, and aspects of insect biology. Additionally, we examine current methods used for calculating PMI based on insects and their development.

Colonization of Blowflies (Diptera: Calliphoridae) and Association Time Between Adults and Immatures in Pig Carcass Decomposition: One Day to Change

Blowflies are often the first to colonize a cadaver, making them valuable forensic indicators for estimating the post-mortem interval (PMI). However, understanding the decomposition process by blowflies in practice presents challenges due to the direct influence of adults and larvae on the process. Environmental factors can either hinder or stimulate colonization by different species, leading to variability across different settings. In this study, we aimed to investigate the variation in the community of adult and immature stages of Calliphoridae blowflies during pig carcass decomposition in an island area of the Amazon rainforest. We identified changes in abundance, richness, and species composition separately for adults and larvae and measured the congruence between larval and adult communities. Our findings revealed that the peak abundance of adults preceded the peak abundance of larvae during carcass decomposition. Eleven species were collected within the first 4 days of decomposition, of which only seven colonized the carcass. Species composition differed between life stages and decomposition phases, with larvae associated with the skeletonization phase and adults with the colliquative phase. The species composition of adults collected from the decomposing carcass corresponded to that of larvae collected 1 day later. This is the first study conducted in an Amazonian island environment in the extreme north of Brazil to document the cadaveric fauna and analyze the congruence between adult and larval communities of blowflies. These insights contribute to forensic entomology understanding and assist forensic professionals, particularly in tropical regions with high rates of unsolved homicides like Brazil.

Influence of Drugs and Toxins on Decomposition Dynamics: Forensic Implications

Drug and toxin-related deaths are common worldwide, making it essential to detect the postmortem concentration of various toxic substances at different stages of decomposition in a corpse. Indeed, determining the postmortem interval (PMI) and cause of death in an advanced stage of decomposed corpses has been a significant challenge in forensic investigations. Notably, the presence of drugs or toxins can have a significant impact on the microbial profile, potentially altering the succession of microbial communities and subsequent production of volatile organic compounds (VOCs), which, in turn, affect insect colonization patterns. This review aims to highlight the importance of investigating the interactions between drugs or toxins, microbial succession, VOC profiles, and insect behavior, which can provide valuable insights into forensic investigations as well as the ecological consequences of toxins occurring in decomposition. Overall, the detection of drugs and other toxins at different stages of decomposition can yield more precise forensic evidence, thereby enhancing the accuracy of PMI estimation and determination of the cause of death in decomposed remains.

Development of Piophila megastigmata (Diptera: Piophilida) at seven constant temperatures

In forensic entomology, the time-related growth and development of carrion insects allows for the estimation of the minimum postmortem interval (PMImin). Piophila megastigmata (Diptera: Piophilidae) is of great significance in estimating PMImin in the late stage of corpse decay. In this paper, the development of P. megastigmata was investigated under the seven constant temperatures of 16-34 °C. The total development time at each temperature was 970.38, 824.50, 593.13, 498.25, 392.00, 385.63 and 405.87 h, respectively. The isomorphen diagram shows the trend of development during different developmental stages at different temperatures. By using a revised linear regression model, the estimated lower lethal developmental thresholds (TL) and thermal summation constant (K) were found to be 10.57 °C and 6936.78 degree hours, respectively. According to a nonlinear model, the TL, upper lethal developmental thresholds (TH), and intrinsic optimum temperature (TΦ) were determined to be 7.53, 34.68, and20.43 °C, respectively. Also, logistic function and an isomegalen diagram were constructed according to the continuous changes in larval body length, and illustrates the time required to develop to a certain length at different temperatures. The obtained results offer crucial fundamental developmental information regarding P. megastigmata, which can be applied in PMImin estimation.

Spatio-Temporal Influence on the Distribution of Forensically Relevant Blowflies (Diptera: Calliphoridae) in Gyeongsangnam-do, South Korea

The study of blowfly (Diptera: Calliphoridae) biodiversity and distribution is crucial for forensic investigations. Abiotic and biotic factors, such as season and habitat type, have a significant impact on blowfly populations. However, only a few forensic entomology studies have been conducted in South Korea, particularly in the Gyeongsangnam-do region. To address this, an extensive year-long survey was conducted to analyze the compositions, habitat preferences, distribution, and seasonal abundance of forensically relevant blowflies in urban and forested habitats of Gyeongsangnam-do, with sampling conducted twice a month using mouse carcass-baited traps set for 48 h each time. A total of 3470 adult blowflies were recorded, encompassing five genera and 13 species, with a noted absence of specimens during the winter months. The predominant species was Lucilia porphyrina, accounting for 37.2% of the total sample, followed by Chrysomya pinguis (27.6%), Lucilia sericata (7.6%), and Lucilia illustris (7.1%). The species composition was consistent across all surveyed regions; however, seasonal variation in species diversity was evident, with a peak in spring and a decline in summer. Notably, certain species exhibited clear preferences for either urban (Calliphora calliphoroides and L. sericata) or forested habitats (L. porphyrina and Ch. pinguis). This pioneering study elucidates the diverse blowfly communities in Gyeongsangnam-do, highlighting significant seasonal and habitat-dependent variations. These findings enrich our understanding of blowfly ecology in this region, offering valuable insights for forensic applications and underscoring the necessity for ongoing entomological surveillance and research.

Simplified COI barcoding of blow, flesh, and scuttle flies encountered in medicolegal investigations

Accurate insect identification is critical to the estimation of time of colonization (TOC) and post-mortem interval (PMI) in medicolegal death investigations. DNA testing is advantageous because it enables the identification of immature specimens that may not be identified based on morphology alone. We describe here a simplified DNA barcoding method for identifying relevant species that may be implemented by forensic genetics laboratories. A cytochrome oxidase (COI) fragment is analyzed after PCR amplification with a single primer set. The method is effective for many species commonly encountered in death investigations in the USA: members of blowfly genera Calliphora, Chrysomya, Cochliomyia, Lucilia, and Phormia; members of the flesh fly genera Blaesoxipha, Oxysarcodexia, Ravinia, and Sarcophaga; and the scuttle fly Megaselia scalaris. We tested the method on specimens with verified identifications and used it to build a collection of reference sequences from specimens collected in Harris County, Texas. We show here the correct identification of larvae, pupae, and pupal exuviae from the medicolegal casework.

The utility of blow fly (Diptera: Calliphoridae) evidence from burned human remains

Burning of human remains is a common method to conceal or destroy evidence associated with homicides and illegal activities. However, data regarding blow fly colonization of burned remains are scarce, with all previously published empirical studies focusing only on non-human animals. It is critically important to obtain basic data on blow fly colonization patterns of burned human remains as such evidence may represent the only feasible method for PMI estimation in cases of burning. In this study, we thermally altered six human donors to a Crow-Glassman Scale Level 3 (CGS-3) and placed them at the Anthropology Research Facility at the University of Tennessee in Summer 2021, Spring 2022, and Summer 2022. Six unburned human donors were used as controls. Observations for insect activity began within 24 h of placement and continued twice weekly through decomposition. Age estimations were performed with immature blow flies to estimate the time of colonization (TOC), and accuracy was assessed against the time of placement for each donor. All burned donors examined in this study were colonized by blow flies. No significant difference in species composition was determined between treatments, though TOC estimations from burned donors were slightly (but significantly) less accurate than TOC estimations from unburned donors (80% vs. 83% accuracy; χ2 = 0.041, df = 1, P = 0.840). These results indicate that blow flies can successfully colonize human remains burned to CGS-3 and that accurate TOC estimations can still be generated from larval specimens. Though several limitations to this study exist (e.g., inconsistent donor BMI, lack of donor temperature data), our results underscore the utility of entomological evidence in cases of burned human remains.

Global change influences scavenging and carrion decomposition

Carrion decomposition is fundamental to nutrient cycling in terrestrial ecosystems because it provides a high-quality resource to diverse organisms. A conceptual framework incorporating all phases of carrion decomposition with the full community of scavengers is needed to predict the effects of global change on core ecosystem processes. Because global change can differentially impact scavenger guilds and rates of carrion decomposition, our framework explicitly incorporates complex interactions among microbial, invertebrate, and vertebrate scavenger communities across three distinct phases of carcass decomposition. We hypothesize that carrion decomposition rates will be the most impacted when global change affects carcass discovery rates and the foraging behavior of competing scavenger guilds.

A novel mathematical model and application software for estimating the age of necrophagous fly larvae

The change in larval body length of necrophagous flies during their development is a key indicator for estimating larval age. However, existing forensic entomological models have limitations in this regard. In this study, a logistic algorithm was used to establish a general model for estimating the minimum postmortem interval (PMImin) using larval body length. The new model was used to simulate the relationship between larval body length and developmental time of eight species of necrophagous flies. The model parameters of body length variation with developmental time of the different species were calculated. Computer software was developed based on the established logistic model. The advantage of the new model is that each parameter has a biological meaning and can be used to estimate the age of larvae at any temperature and any larval body length. Cross-validation of the model showed that the overall mean accuracy of the fitted growth curves for the eight necrophagous fly larvae was 82.7%, the mean accuracy of age extrapolations for seven necrophagous fly species ranged from 76.8% to 92.9%, while the accuracy of age extrapolations for only one species was lower (i.e., 63.3%). This study provides a new method to estimate the PMImin based on larval body length, and the developed computer software will facilitate its application in forensic entomology.

Development of Megaselia scalaris at constant temperatures and its significance in estimating the time of death

Megaselia scalaris (Schmitz, 1938) (Diptera: Phoridae) is a common insect in forensic science that is frequently found in indoor cases, particularly on corpses in closed environments. Although this species is useful for estimating the minimum postmortem interval (PMImin) in the absence of Calliphoridae, there is a lack of data on its development in China. Herein, we studied the development of M. scalaris exposed to seven constant temperatures ranging from 16 to 34 °C. The mean (± SD) developmental durations of M. scalaris from egg to adult stage at 16, 19, 22, 25, 28, 31, and 34 °C were 1486.9 ± 75.3, 823.7 ± 42.8, 448.2 ± 59.8, 417.7 ± 19.7, 297.2 ± 27.3, 272.9 ± 10.4, and 253.0 ± 5.0 h, respectively. The mean (± SE) lower developmental threshold temperature (TL) and the thermal summation constant (K) were determined by a linear model as 12.69 ± 0.3 °C and 4965.8 ± 227.9-degree hours, respectively. A nonlinear model estimated the lower developmental threshold temperature, intrinsic optimum temperature, and upper lethal developmental threshold temperature as 14.58, 21.00, and 34.15 °C, respectively. We established three development models to estimate the age of the immature insect, namely the isomegalen diagram, isomorphen diagram, and thermal summation model. In addition, a regression analysis of the relationship between body length and total development time from hatching to pupariation was performed. Our findings provide a basis for applications of M. scalaris in PMImin estimations.

Geographical Distribution and Multimethod Species Identification of Forensically Important Necrophagous Flies on Hainan Island

Forensic entomology offers unique advantages for the minimum postmortem interval (PMImin) estimation of decomposed corpses in forensic investigations. Accurate species identification and up-to-date locality information are essential. Hainan Island has a tropical rainforest climate and a vast territory. In this study, the community structure of necrophagous flies on Hainan Island was investigated in detail according to geographical environment. The results showed that the dominant species included C. megacephala, S. peregrina, C. rufifacies, S. misera, H. ligurriens, S. sericea, S. cinerea, S. dux, C. pinguis, and M. domestica. Furthermore, C. rufifacies and C. villeneuvi were found only in the high-altitude areas of Wuzhi Mountain, while S. cinerea was distributed only in coastal areas; the latter is a representative species of Hainan Island and has not been reported before. Furthermore, a GenBank database of forensically important flies was established, whilst a high-resolution melt (HRM) curve analysis was applied to identify the common species of Hainan Island for the first time. This study enriches the database of forensically important flies in tropical rainforest regions.

Application of omics techniques in forensic entomology research

With the advent of the post-genome era, omics technologies have developed rapidly and are widely used, including in genomics, transcriptomics, proteomics, metabolomics, and microbiome research. These omics techniques are often based on comprehensive and systematic analysis of biological samples using high-throughput analysis methods and bioinformatics, to provide new insights into biological phenomena. Currently, omics techniques are gradually being applied to forensic entomology research and are useful in species identification, phylogenetics, screening for developmentally relevant differentially expressed genes, and the interpretation of behavioral characteristics of forensic-related species at the genetic level. These all provide valuable information for estimating the postmortem interval (PMI). This review mainly discusses the available omics techniques, summarizes the application of omics techniques in forensic entomology, and their future in the field.

Seasonal distribution of Calliphoridae and Mesenbrinellidae (Diptera) associated with the decomposition of a clothed animal model in a forest reserve in the Central Amazon

We evaluated the effects of seasonality on the richness and abundance of dipterans of the families Calliphoridae and Mesembrinellidae associated with the decomposition of a clothed Large White swine Sus scrofa domesticus(Artiodactyla: Suidae) carcass. Experiments were carried out in less rainy, rainy, and intermediate periods between 2010 and 2011 at Reserva Florestal Ducke, Manaus, Amazonas. Two pig carcasses, each weighing approximately 40 kg, were used in each period. A total of 63,872 individuals of 18 species of Calliphoridae and Mesembrinellidae were collected. The abundance and richness of these dipteran families were influenced by the interaction between period and decomposition stage. The compositions of the Calliphoridae and Mesembrinellidae assemblages differed among periods, with the fauna of the less rainy period being less similar to those of the intermediate and rainy periods than they were to each other. Three species were selected as indicators for the less rainy period, namely Paralucilia pseudolyrcea (Mello, 1969) (Diptera, Calliphoridae), Paralucilia nigrofacialis (Mello, 1969) (Diptera, Calliphoridae), and Eumesembrinella randa (Walker, 1849) (Diptera,Mesembrinellidae) while Chloroprocta idioidea (Robineau-Desvoidy, 1830) (Dipetra, Calliphoridae) was selected as an indicator species for the rainy period; no taxon was selected as an indicator of the intermediate period. Among decomposition stages, only fermentation and black putrefaction had indicator taxa, with Hemilucilia souzalopesi Mello, 1972 (Diptera, Calliphoridae and Chysomya putoria(Wiedemann, 1830) (Diptera, Calliphoridae), respectively. Clothes did not prevent the laying of eggs and became a kind of protection for immature stages. The clothed model presented a delay in decomposition compared to other studies developed in the Amazon region.

A synthesis of carcass decomposition studies conducted at a tropical (Aw) taphonomy facility: 2013-2022

Decomposition studies have been conducted in several regions of the world, but relatively few have investigated taphonomy in tropical environments. Even fewer have explored carcass decomposition during multiple tropical seasons, leaving the relationships between season and decomposition in tropical environments poorly understood. Ten decomposition studies using 30 carcasses were conducted in Honolulu, Hawaii, USA to start addressing this knowledge gap. These studies show that some postmortem processes were observed regardless of season. Carcass temperature and chemistry were spatiotemporally variable. Fly larval masses were consistently observed within 3 days (∼75 ADD) postmortem and carcasses lost 60%-90% of mass by 10 days (∼250 ADD) postmortem (Total Body Score ∼26). Season had a significant effect on decomposition, yet the warmest and most humid seasons did not always result in the most rapid and extensive decomposition. Seasonal variation appears to be less pronounced than at other tropical decomposition sites.

How Rearing Systems for Various Species of Flies Benefit Humanity

Flies (Diptera) have played a prominent role in human history, and several fly species are reared at different scales and for different beneficial purposes worldwide. Here, we review the historical importance of fly rearing as a foundation for insect rearing science and technology and synthesize information on the uses and rearing diets of more than 50 fly species in the families Asilidae, Calliphoridae, Coelopidae, Drosophilidae, Ephydridae, Muscidae, Sarcophagidae, Stratiomyidae, Syrphidae, Tachinidae, Tephritidae, and Tipulidae. We report more than 10 uses and applications of reared flies to the well-being and progress of humanity. We focus on the fields of animal feed and human food products, pest control and pollination services, medical wound therapy treatments, criminal investigations, and on the development of several branches of biology using flies as model organisms. We highlight the relevance of laboratory-reared Drosophila melanogaster Meigen as a vehicle of great scientific discoveries that have shaped our understanding of many biological systems, including the genetic basis of heredity and of terrible diseases such as cancer. We point out key areas of fly-rearing research such as nutrition, physiology, anatomy/morphology, genetics, genetic pest management, cryopreservation, and ecology. We conclude that fly rearing is an activity with great benefits for human well-being and should be promoted for future advancement in diverse and innovative methods of improving existing and emerging problems to humanity.

A Summary of Concepts, Procedures and Techniques Used by Forensic Entomologists and Proxies

Forensic entomology is a branch of forensic science that incorporates insects as a part of solving crime. Insect-based evidence recovered at a crime scene can be used to estimate the minimum postmortem interval, determine if a carcass/corpse has been relocated, and contribute to the cause and manner of death. The current review summarises the stepwise usage of forensic entomology methods at a crime scene and in the laboratory, including specimen collection and rearing, identification, xenobiotic detection, documentation, and referencing previous research and casework. It also provides three standards for the collection of insects when attending a crime scene. The Gold standard attributes to a forensic entomologist (FE) who is likely to be well-trained attending a scene. The subsequent standards (Silver and Bronze) have been added because the authors believe that this information is currently missing in the literature. The purpose is so that an attending crime scene agent/proxy with some basic knowledge and some simple tools can recover almost all the insect information required by an FE to make the best estimation of the minimum postmortem interval.

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.

Case closed - Wrappings and encasement delays and reduces fly presence on body parts

Homicide, particularly where a body has been concealed, is uniquely challenging for investigators to estimate the time of occurrence due to the methods employed by perpetrators to hide the body or its constituent parts from detection. The regularity of necrophagous insect lifecycles to determine minimum post-mortem interval (minPMI) is widely employed but remains an unreliable technique if used without a clear understanding of the factors that affect insect access and oviposition behaviour to concealed remains. The purpose of this study was to investigate the effect of wrapping body parts on fly colonisation and implications for minPMI calculations. Field studies were carried out using four treatments of pork (as surrogate body parts), in five replicates, one unwrapped, the other three wrapped in either a black plastic sack, a small-zipped wash bag (to simulate a suitcase), or a plastic sack further placed in a wash bag. Over a 48-h period all the methods of wrapping significantly disrupted the host-finding process of blowflies to dismembered carcasses, with a delay of initial contact and oviposition of 30+h (dependant on wrapping) and even more in wet conditions (48+ h). Egg numbers were also reduced by as much as 99.1% on wrapped samples compared to unwrapped. These new findings highlight the importance of applying adjustments to minPMI calculations when encountering wrapped remains. Advances in the accuracy of minPMI calculations will prevent the waste of valuable police time and resources and better focus the search for witnesses and suspects in homicide investigations.

Effects of Tissue Type and Temperature on Selected Life-History Traits of the Flesh Fly, Sarcophaga crassipalpis (Macquart, 1839) (Diptera: Sarcophagidae)

The flesh fly, Sarcophaga crassipalpis Macquart 1839 (Diptera: Sarcophagidae), colonizes estimation of the minimum post-mortem interval (min-PMI). This study examined the effects of different types of tissues and temperature on the development of S. crassipalpis. To the best of our knowledge, the present study is the first to investigate the effects of life-history information of S. crassipalpis. Larvae were reared on three tissue types, chicken heart, bovine minced meat, and bovine tongue, at five temperatures, 15, 20, 25, 30, and 32°C. Pupal and larval development time, adult weight, and pupal and larval survival differed significantly for tissue type and temperature. Temperature had a significant effect on pupal weight but tissue type did not significantly affect pupal weight. The duration of the larval and pupal stages (except of chicken heart, 30°C) decreased with increasing temperature, except for 32°C, in all tissue types. Larval survival was lowest at 32°C in bovine minced meat, bovine tongue, and chicken heart, and at 32°C, all pupae failed to reach the adult stage in minced meat. The results of this study highlight the necessity of considering larval diet and temperature in forensic investigations.

Microbial communities in the liver and brain are informative for postmortem submersion interval estimation in the late phase of decomposition: A study in mouse cadavers recovered from freshwater

INTRODUCTION

Bodies recovered from water, especially in the late phase of decomposition, pose difficulties to the investigating authorities. Various methods have been proposed for postmortem submersion interval (PMSI) estimation and drowning identification, but some limitations remain. Many recent studies have proved the value of microbiota succession in viscera for postmortem interval estimation. Nevertheless, the visceral microbiota succession and its application for PMSI estimation and drowning identification require further investigation.

METHODS

In the current study, mouse drowning and CO2 asphyxia models were developed, and cadavers were immersed in freshwater for 0 to 14 days. Microbial communities in the liver and brain were characterized via 16S rDNA high-throughput sequencing.

RESULTS

Only livers and brains collected from 5 to 14 days postmortem were qualified for sequencing. There was significant variation between microbiota from liver and brain. Differences in microbiota between the cadavers of mice that had drowned and those only subjected to postmortem submersion decreased over the PMSI. Significant successions in microbial communities were observed among the different subgroups within the late phase of the PMSI in livers and brains. Eighteen taxa in the liver which were mainly related to Clostridium_sensu_stricto and Aeromonas, and 26 taxa in the brain which were mainly belonged to Clostridium_sensu_stricto, Acetobacteroides, and Limnochorda, were selected as potential biomarkers for PMSI estimation based on a random forest algorithm. The PMSI estimation models established yielded accurate prediction results with mean absolute errors ± the standard error of 1.282 ± 0.189 d for the liver and 0.989 ± 0.237 d for the brain.

CONCLUSIONS

The present study provides novel information on visceral postmortem microbiota succession in corpses submerged in freshwater which sheds new light on PMSI estimation based on the liver and brain in forensic practice.

Identification and Characterization of Small RNA Markers of Age in the Blow Fly Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae)

Blow fly development is important in decomposition ecology, agriculture, and forensics. Much of the impact of these species is from immature samples, thus knowledge of their development is important to enhance or ameliorate their effects. One application of this information is the estimation of immature insect age to provide temporal information for death investigations. While traditional markers of age such as stage and size are generally accurate, they lack precision in later developmental stages. We used miRNA sequencing to measure miRNA expression, throughout development, of the secondary screwworm, Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae) and identified 217 miRNAs present across the samples. Ten were identified to be significantly differentially expressed in larval samples and seventeen were found to be significantly differentially expressed in intrapuparial samples. Twenty-eight miRNAs were identified to be differentially expressed between sexes. Expression patterns of two miRNAs, miR-92b and bantam, were qPCR-validated in intrapuparial samples; these and likely food-derived miRNAs appear to be stable markers of age in C. macellaria. Our results support the use of miRNAs for developmental markers of age and suggest further investigations across species and under a range of abiotic and biotic conditions.

Not by the Book: Observations of Delayed Oviposition and Re-Colonization of Human Remains by Blow Flies

Postmortem interval estimations can be complicated by the inter-individual variation present in human decomposition. Forensic entomologists may especially face challenges interpreting arthropod evidence in scenarios that are not "by the book", or that vary in unexpected ways. Therefore, it is important to report instances where blow fly colonization does not align with expected soft tissue decomposition as blow fly larvae are often used to produce a time of colonization (TOC) estimation to infer a minimum PMI. We followed the decomposition and blow fly activity of three human donors at the Anthropology Research Facility (University of Tennessee). Delayed oviposition occurred on one donor 115 d post-placement, whereas two donors experienced blow fly re-colonization after cessation of the consumption phase, one 22 d and one more than 200 d after blow fly larvae were last observed. A null hypothesis model tested whether the entomological TOC and anthropological total body score (TBS) estimations encompassed the time of placement (TOP) for each donor. While the null hypothesis was rejected for all TOC estimations, it could not be rejected for the TBS estimations. We discuss how the non-linear nature of human decomposition can pose challenges to interpreting blow fly evidence and suggest that forensic entomology practitioners should recognize these limitations in both research endeavors and applied casework.

Linking bacteria, volatiles and insects on carrion: the role of temporal and spatial factors regulating inter-kingdom communication via volatiles

Multi-kingdom community complexity and the chemically mediated dynamics between bacteria and insects have recently received increased attention in carrion research. However, the strength of these inter-kingdom interactions and the factors that regulate them are poorly studied. We used 75 piglet cadavers across three forest regions to survey the relationship between three actors (epinecrotic bacteria, volatile organic compounds (VOCs) and flies) during the first 4 days of decomposition and the factors that regulate this interdependence. The results showed a dynamic bacterial change during decomposition (temperature-time index) and across the forest management gradient, but not between regions. Similarly, VOC emission was dynamic across a temperature-time index and the forest management gradient but did not differ between regions. However, fly occurrence was dynamic across both space and time. The strong interdependence between the three actors was mainly regulated by the temperature-time index and the study regions, thereby revealing regulation at temporal and spatial scales. Additionally, the actor interdependence was stable across a gradient of forest management intensity. By combining different actors of decomposition, we have expanded our knowledge of the holistic mechanisms regulating carrion community dynamics and inter-kingdom interactions, an important precondition for better describing food web dynamics and entire ecosystem functions.

Temporal Expression Profiles Reveal Potential Targets during Postembryonic Development of Forensically Important Sarcophaga peregrina (Diptera: Sarcophagidae)

Sarcophaga peregrina (Robineau-Desvoidy, 1830) is a species of medical and forensic importance. In order to investigate the molecular mechanism during postembryonic development and identify specific genes that may serve as potential targets, transcriptome analysis was used to investigate its gene expression dynamics from the larval to pupal stages, based on our previous de novo-assembled genome of S. peregrina. Totals of 2457, 3656, 3764, and 2554 differentially expressed genes were identified. The specific genes encoding the structural constituent of cuticle were significantly differentially expressed, suggesting that degradation and synthesis of cuticle-related proteins might actively occur during metamorphosis. Molting (20-hydroxyecdysone, 20E) and juvenile (JH) hormone pathways were significantly enriched, and gene expression levels changed in a dynamic pattern during the developmental stages. In addition, the genes in the oxidative phosphorylation pathway were significantly expressed at a high level during the larval stage, and down-regulated from the wandering to pupal stages. Weighted gene co-expression correlation network analysis (WGCNA) further demonstrated the potential regulation mechanism of tyrosine metabolism in the process of puparium tanning. Moreover, 10 consistently up-regulated genes were further validated by qRT-PCR. The utility of the models was then examined in a blind study, indicating the ability to predict larval development. The developmental, stage-specific gene profiles suggest novel molecular markers for age prediction of forensically important flies.

Characterized Gene Repertoires and Functional Gene Reference for Forensic Entomology: Genomic and Developmental Transcriptomic Analysis of Aldrichina grahami (Diptera: Calliphoridae)

Many flies of Diptera are common entomological evidence employed in forensic investigation. Exploring the existence of inter- and intra-species genomic differences of forensically relevant insects is of great importance. Aldrichina grahami is a common blow fly species of forensic importance. The present study characterized the gene repertoires of A. grahami, and provides insights into issues related to forensic entomology, such as necrophagous behavior, gene family features, and developmental patterns. Gene families were clustered and classified according to their function in different aspects of the necrophagous lifestyle, generating several gene repertoires. The genes under positive selection pressure and evolutionary changes were screen and identified. Moreover, genes that exhibited potential prediction value in the post mortem interval (PMI) estimation and development of immature stages were subjected to analysis based on the developmental transcriptome. Related insect species were compared at the genomic level to reveal the genes associated with necrophagous behaviors. The expression of selected genes in separated repositories was verified using qPCR. This work was conducted using a high-quality chromosome-level genome assembly of A. grahami and its developmental transcriptome. The findings will facilitate future research on A. grahami and the other forensically important species.

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.

Rodent scavenging of pig remains potentially increases oviposition sites for primary colonizers

The feeding of vertebrate scavengers on animal remains has been noted for at least 30 years in relation to the creation of postmortem artifacts. However, the subsequent impact on other necrophagous arthropods, which interact with these remains has not been well documented. Herein, we report a rodent (Rattus spp.) feeding event that altered a perimortem wound beneath the jaw of a decomposing swine carcass. Point trauma such as this has been cited as insufficient for insect colonization; however, the resulting enlargement of the wound due to scavenger feeding has the potential to serve as an oviposition site where colonization would typically not be expected otherwise (i.e., in the absence of a wound or the presence of a small wound such as point trauma). In fact, colonization was observed surrounding the site of scavenger alteration. If scavenger artifacts (e.g., postmortem alteration of remains by feeding) are not identified appropriately and recognized for the effects they may have on necrophagous arthropods then associated assessments in forensic investigations could be affected.

Biodiversity of Forensically Relevant Blowflies (Diptera: Calliphoridae) at the Anthropology Research Facility in Knoxville, Tennessee, USA

Understanding the biodiversity and distribution of forensically relevant blowflies (Diptera: Calliphoridae) in a region can aid in legal investigations when insects are associated with remains. For this purpose, we conducted a 14-month-long blowfly survey at the Anthropology Research Facility (ARF) of the University of Tennessee in Knoxville, Tennessee. Traps baited with pork kidney were deployed for 24 h twice a month throughout the study. A total of 3180 adult blowflies were collected, comprising 13 species from 7 genera. Phormia regina (Meigen) and Lucilia coeruleiviridis (Macquart) were the predominant species collected from this survey, with collections representing 65.9% and 20.6%of total flies captured, respectively. In addition to relative abundance, we investigated blowfly community composition, species abundance, richness, and diversity by season. One state record was identified, with adult Protophormia terraenovae (Robineau-Desvoidy) being collected for the first time in Tennessee. Additionally, an earlier record of Chrysomya megacephala (Fabricius) in Tennessee was noted. These findings can be used to aid in legal investigations in the area and surrounding areas where work is limited, as well as to provide information on which forensically relevant species should be the subject of future research in the area.

Calliphoridae (Diptera) on Decomposing Pig Carcasses and Human Cadavers in the Upper Midwest of North America

The geographic ranges of forensically informative taxa on decomposing remains vary across regions. To determine which calliphorid flies would be expected to occur in Minnesota and the upper Midwest, individual freshly killed pig carcasses (Sus scrofa L.) were placed in the field in St. Paul, MN, at monthly intervals from May to October 2017 and May to September 2018. Aerial nets, forceps, and pitfall traps were used to collect and preserve associated adult and immature insects. Sixty-four forensically informative insect taxa were recorded, representing three insect orders and 14 families. Ten informative calliphorid species were recorded on carcasses, adding four new Minnesota records. Comparison of species lists from 26 human forensic cases indicated agreement between the two lists, except for Lucilia coeruleiviridis Macquart, Calliphora vomitoria (L.), and Cynomya cadaverina Robineau-Desvoidy, which occurred on pig carcasses but not human remains, and Calliphora livida Hall, which occurred on human remains, but not carcasses. The composite fauna list from cadavers agreed largely with the 2-yr list from pig carcasses.

Dynamics of insects, microorganisms and muscle mRNA on pig carcasses and their significances in estimating PMI

The accurate estimate of the postmortem interval (PMI) is of vital significance in the investigation of homicide cases. In this study, three pig carcasses were placed in the field to study the pattern of insect succession, the change of microorganisms and the degradation of muscle tissue RNA during the decomposition process. The results showed that insects could quickly colonize the carcasses and still exist on them until the end of the experiment (41 days). Their development and succession patterns are useful indicators for PMI estimation. The diversity of rectal microorganisms decreased with the decomposition time. In different decomposition periods, significant differences in the rectal and soil microbial composition and relative abundance were found, which could be used to estimate the PMI with an accuracy of 3-4 days. The RNA of muscle tissue was found to have a time-dependent relationship with the PMI. Ppia and Gapdh showed a linear upward trend within 10 h after the death, followed by a gradual downward trend from 10 to 240 h. The expression of β-actin gene showed a gradual downward trend during 0-240 h. This is the first study in China to analyze the changes of insects, muscle RNA and microorganisms on pig carcasses in the same natural environment, which provide basic data for the PMI estimation.

The Effects of Gunshot Residue Components (Pb, Ba, and Sb) on the Life History Traits of Lucilia sericata (Diptera: Calliphoridae)

The present study aimed to investigate the impact of gunshot residue (GSR) components (Pb, Sb, and Ba) on the life history parameters of Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae). This experiment was carried out at the Zoology Department, the Ondokuz Mayıs University in 2020. About 50 larvae, respectively were exposed to the chicken liver with four different concentrations of GSR particles and life history parameters recorded. A two-way analysis of variance (Two way ANOVA) was used on the larval weight, and length, development time, percentage of pupal and larval survival. Pearson's correlation coefficient was used to assess the association between life-history parameters and the concentration of GSR. The total development times decreased with increasing Sb, Ba, and Pb concentrations in the diets 1-3 d when compared to the control The results showed that Ba and Sb significantly decreased larval and pupal survival and GSR decreased the pupa and adult weight as compared to the control. We concluded that life-history parameters of L. sericata are sensitive to GSR residue and heavy metal changes in the environment. The presence of gunshot residue in the corpse should be kept in mind in a criminal investigation.

The time of death in Dutch court; using the Daubert criteria to evaluate methods to estimate the PMI used in court

When a capital crime is committed the post-mortem interval (PMI) is of particular importance in investigating a suspect's alibi in court. A forensic expert can use different methods to estimate the PMI. This research focuses on who is considered an expert in court and whether the methods used to estimate the PMI are reliable. In this study, the methods used to estimate the PMI and the experts consulted, available in Dutch jurisprudence, in the period 2010-2019 were investigated. Ninety-four judicial cases were included and multiple experts and methods of estimating the PMI were found. As part of this study, the methods that were used to estimate the PMI in court were subjected to the Daubert criteria. Of these methods, only the Henssge nomogram and entomological methods met the Daubert criteria. However, the methods are only useful when applied by the right forensic expert and in the right manner. Unfortunately, this was not always the case.

Forensically relevant blow flies (Diptera: Calliphoridae) of Central Connecticut, USA

Connecticut and the Northeastern United States in general, lacks forensically relevant entomological survey data. To determine which forensically relevant calliphorid (blow flies, Diptera: Calliphoridae) and non-calliphorid species dominate Connecticut, 5 traps using pork bait were set out 7 times over a 2-year period to collect adult and immature specimens. Insects collected from human corpses in this region were also tabulated to collaborate the forensic relevance of trapped specimens. The survey identified a total of 8 species of blow flies of the Lucilia and Calliphora genera, 6 of which colonized the baits, and 5 of which have been found to colonize human corpses in the area. Non-calliphorid genera Sarcophaga and Muscina were also found to be colonizers of the baited traps but in relatively lower numbers. Trap sites differed significantly in the degree of urbanization which was determined by using GIS mapping to classify a 1 kilometer (km) radius around each site using land use and the percent of urban impervious surfaces. The 1 km radius revealed the highly fragmented nature of the immediate habitats of the trap sites and no habitat or seasonal preference was demonstrated by blow flies under these trap conditions. Temperature was the one variable which significantly affected the number of flies trapped and the colonizing species. All trapped species have been described previously as widespread and common in the United States and as synanthropic. Further research in this region should trap at the constantly changing extreme ends of the urban-rural gradient and in the colder temperatures of winter to explore the limits of the flexibility of these blow fly species.

Exploring microbial communities, assessment methodologies and applications of animal's carcass decomposition: a review

Animals are an essential part of the ecosystem, and their carcasses are the nutrient patches or hotspots where nutrients accumulate for a long time. After death, the physical and chemical properties undergo alterations inside the carcass. The animal carcass is decomposed by many decomposers such as bacteria, fungi, microeukaryotes and insects. The role of microbial symbionts in living organisms is well explored and studied, but there is a scarcity of knowledge and research related to their role in decomposing animal carcasses. Microbes play an important role in carcass decomposition. The origins of microbial communities associated with a carcass, including the internal and external microbiome, are discussed in this review. The succession and methods used for the detection and exploration of decomposition-associated microbial communities have been briefly described. Also, the applications of carcass-associated microbial taxa have been outlined. This review is intended to understand the dynamics of microbial communities associated with the carcass and pave the way to estimate postmortem interval and its role in recycling nutrients.

Habitat Associations of Carrion Beetles (Coleoptera: Silphidae) Across a Full Annual Cycle

Necrophagous insects play an important role in decomposition and nutrient recycling of decomposing vertebrates. Ecological studies of carrion-associated beetles enhance forensic investigations by providing information about community assemblages and predictable patterns of succession. However, lack of standardized protocols that include replication, spatial scale, and phenology reduce detection of patterns and predictions. To address these gaps and examine the influence of habitat (woodlands vs grasslands) and abiotic factors on carrion beetle (Coleoptera: Silphidae) communities, we developed an experimental approach from broad to finer scale located within the Kansas Flint Hills across a full annual cycle (12 contiguous months). In total, 3,333 adult carrion beetles in nine species were collected from pitfall traps baited with rat carrion over thirteen 4-wk collecting periods. PERMANOVA and NMDS demonstrate that the silphid beetle community was significantly different in species composition between grassland and woodland habitats, but communities did not differ significantly in overall mean abundance, mean species richness, or mean species diversity. Two species exhibited strong habitat associations; one associated with grassland habitat (Nicrophorus marginatus F.) and one with woodland habitat (Nicrophorus orbicollis Say). Our results reveal that habitat associations of silphid beetles can be useful in forensic investigations by determining corpse relocation and in ecological studies that explore niche filtering.

Optimizing a Dual-Choice Cube Olfactometer Design for Measuring Adult Secondary Screwworm (Diptera: Calliphoridae) Attraction to a Resource

Detecting and locating a carrion resource is critical for the reproduction of necrophagous insects and initiating forensically important timelines. Blow flies (Diptera: Calliphoridae) primarily use olfactory cues in the form of volatile organic compounds to locate a suitable resource. Factors governing detecting and locating a resource have been studied using various behavior assays with modifications to suit the experiment design, such as the dual-choice cube olfactometer, which was examined in the current study. Systems optimization ensures biologically relevant and consistent results across replicates. In this study, two responses were measured: 1) leaving cube for either control or treatment and 2) choice between control and treatment. Phenotype (e.g., male, non-gravid, gravid) and total blow fly, Cochliomyia macellaria (Fabricius) (Diptera: Calliphoridae), number to respond were measured. Four parameters were assessed for their impact on response: 1) adjustment time in cube before trial, 2) trial length, 3) sugar/water presence, and 4) screening type in arms. Approximately, 70% of all phenotypes responded to liver with the 30-min adjustment period where only 50% responded with other adjustment periods. Trial length had a significant impact on response (35% increase in the 8 h trial compared to shorter durations); however, significant response to treatment was lost by increasing trial length. The presence of sugar/water decreased gravid and non-gravid response by 35% but did not impact males. Screening had no influence on overall or treatment response. Data indicate experiment design impacts fly response. Future studies should optimize parameters for their given fly population prior to initiating experiments.

Body Size and Cuticular Hydrocarbons as Larval Age Indicators in the Forensic Blow Fly, Chrysomya albiceps (Diptera: Calliphoridae)

Chrysomya albiceps (Wiedemann 1819) is one of the most important insects in forensic entomology. Its larval developmental and survival rates are influenced by nutritional resources, temperature, humidity, and geographical regions. The present study investigated the possibility of relying on body size and cuticular hydrocarbon composition as indicators for age estimation of the different larval instars of C. albiceps. Larvae were maintained in standardized laboratory conditions at different experimental temperatures. All larval instars (first, second, and third) were randomly collected for measuring their body sizes and for estimating their cuticular hydrocarbons at different rearing temperatures (30, 35, 40, and 45°C) using gas chromatography-mass spectrometry (GC-MS). Results indicated that the duration of larval stage was temperature dependent as it gradually decreased on increasing the rearing temperature (30, 35, and 40°C) except 45°C at which larval development was ceased. In contrary, larval body size, in terms of length, width, and weight, was temperature dependent as it gradually increased with larval development on increasing rearing temperature except at 45°C at which larval development was ceased. The GC-MS showed a significant difference in the extracted components of cuticular hydrocarbons between different larval instars reared in the same temperature and between the same larval instar that reared at different temperatures. Furthermore, the highest and lowest amounts of cuticular hydrocarbons were detected at 35 and 40°C, respectively. Overall, larval body size and cuticular hydrocarbon components were temperature dependent within the range 30-40°C, which may suggest them as possible reliable age indicators for estimating the postmortem interval in the field of medicolegal entomology.

The Forensic Entomology Case Report-A Global Perspective

Forensic practitioners analyzing entomological evidence are faced with numerous challenges when presenting their findings to law practitioners, particularly in terms of terminology used to describe insect age, what this means for colonization time of remains, and the limitations to estimates made. Due to varying legal requirements in different countries, there is no standard format for the entomological case report prepared, nor any guidelines as to the sections that are required, optional or unnecessary in a case report. The authors herein propose sections that should be considered when drafting an entomological case report. The criteria under which entomological evidence is analyzed are discussed, as well as the limitations for each criterion. The concept of a global, standardized entomological case report is impossible to achieve due to national legislative differences, but the authors here propose a basic template which can be adapted and changed according to the needs of the practitioner. Furthermore, while the discussion is fairly detailed, capturing all differences between nations could not be accomplished, and those initiating casework for the first time are encouraged to engage other practicing forensic entomologists or professional associations within their own nation or region, to ensure a complete report is generated that meets lab or national requirements, prior to generating a finalized report.

Microbiome in Death and Beyond: Current Vistas and Future Trends

Forensic medicine has, for a long time, been relying on biochemical, anthropologic, and histopathologic evidences in solving various investigations. However, depending on the method used, lengthy sample processing time, scanty sample, and less sensitivity and accuracy pervade these procedures. Accordingly, newer arenas such as the thanatomicrobiome have come forward to aid in its quandaries; furthermore, the parallel advances in genomic and proteomic techniques have complemented and are still emerging to be used in forensic experiments and investigations. Postmortem interval (PMI) is one of the most important aspects of medico-legal investigations. The current trend in PMI estimation is toward genomic analyses of autopsy samples. Similarly, determination of cause of death, although a domain of medical sciences, is being targeted as the next level of forensic casework. With the current trend in laboratory sciences moving to the discovery of newer disease-specific markers for diagnostic and prognostic purposes, the same is being explored for the determination of the cause of death by using techniques such as Real-Time PCR, DNA micro-array, to Next-Gen Sequencing. Establishing an individual’s biological profile has been done using medicolegal methods and anthropology as well as bar-bodies/Davidson bodies (gender determination); and in cases where the determination of age/gender is a challenge using morphological characteristics; the recent advances in the field of genomics and proteomics have played a significant role, e.g., use of mitochondrial DNA in age estimation and in maternity disputes. The major hurdle forensic medical research faces is the fact that most of the studies are conducted in animal models, which are often difficult to mimic in human and real-time scenarios. Additionally, the high accuracy required in criminal investigations to be used in a court of law as evidence has prevented these results to come out of the labs and be used to the optimum. The current review aims at giving a comprehensive and critical account of the various molecular biology techniques including “thanatogenomics,” currently being utilized in the veritable fields of forensic medicine.