Minimum Postmortem Interval Research Articles

Challenges of the minimum postmortem interval (PMImin) estimation in forensic scenarios: Is dental histology an alternative?

Postmortem interval (PMI) estimates the time since death. Teeth are perennial elements capable of remaining intact in taphonomic environmental circumstances. The objective was to evaluate the feasibility of estimating the minimum postmortem interval (PMImin) through histological analyses of dental tissues exposed to burial and drowning conditions, simulating common scenarios in forensic practice. A total of n = 99 teeth were analyzed and divided into four groups: control (T0), one month (T1), three months (T2), and six months (T3). The control sample comprised 10 teeth, while T1, T2 e T3 were divided into three different subgroups: controlled environment, buried, and drowned. For each subgroup, ten samples were used. Following exposure to taphonomic conditions, the specimens were processed, and histological sections were obtained. The two-way ANOVA test and the Tukey’s post-hoc test were employed for the quantitative analysis of dentin collagen fibrils, revealing statistically significant differences (α = 5 %). This allowed for the estimation of the PMImin at three months by observing pixel counts exceeding 13e+05 in drowned teeth and greater than 8e+05 in buried teeth. Qualitative analysis revealed that the PMImin of drowned teeth was estimated at one month due to the absence of the periodontal ligament (PDL) and at six months due to the absence of predentin and partial degradation of the cementum. For buried teeth, the three-month PMImin was indicated by the absence of PDL and partial cementum degradation. The absence of pulp and remnants of predentin characterized the six-month PMImin. Qualitative and quantitative histological characteristics and parameters are potential to estimate PMImin in forensic scenarios spanning up to six months.

Post-mortem interval determinations using insects collected from illegally hunted and dehorned rhinoceros in the Republic of South Africa from 2014 to 2021.

Wildlife forensic science is a growing research field globally with application in criminal cases of illegal hunting requiring an estimate of time of death based on insect fauna. The techniques and procedures of forensic entomology acquired over the last 40 years, used in legal cases relating to human remains, can be adapted to decomposing wildlife. Research on carrion utilising the rate of development of insect immatures provides a biological clock from which a minimum post-mortem interval (minPMI) can be derived. The following study concerns 19 rhinoceros that were illegally killed and dehorned in the Republic of South Africa between 2014 and 2021. The paper details 74 samples of insect evidence collected from these rhinoceros remains from which an accurate estimate of their PMI was calculated. The specimens comprised 18 species from 12 families belonging to three insect orders. Many Dipteran and Coleopteran species were found on and around each carcass. The species of fly larvae (family Calliphoridae) used in each case to estimate the PMI are as follows: Chrysomya marginalis (Wiedemann) (13 cases), Chrysomya chloropyga (Wiedemann) (2 cases), Chrysomya albiceps (Wiedemann) (1 case) and Chrysomya megacephala (Fabricius) (1 case). Two species of Coleoptera from the family Dermestidae and Silphidae involved Dermestes maculatus (DeGeer) and Thanatophilus micans (Fabricius), respectively, also were involved in one PMI estimation each. The paper highlights opportunities for improving our global understanding of gaps in procedures and training related to wildlife criminal cases.

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.

Exploring unified methods of killing and storing insect samples for forensic entomotoxicology using diazepam in Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) larvae

Forensic entomologists use the maturity of necrophagous larvae to estimate the minimum post-mortem interval (PMImin), ideally taking account of effects that xenobiotics in the corpse may have on insect maturation. Forensic toxicologists may employ larvae to detect drugs in drug-related deaths when human samples are unavailable. Yet current pre-analytical practices of these two professions differ significantly, impeding the successful use of the same samples. Potential benefits of shared pre-analytical practices and opportunities for enhanced collaboration have yet to be fully explored. We employed Lucilia sericata (Meigen, 1826) (Diptera: Calliphoridae) larvae, grown in the presence of diazepam, to investigate the effects of two standard investigative practices on larvae for drug detection and for quantifying mass and length as proxies of age. Specimens were killed by either blanching or freezing and stored at -20℃ for either intermediate or long periods. Blanched larvae showed smaller changes in size and body integrity during storage, thereby producing the most reproducible estimates of PMImin. Consequently, data obtained from blanched larvae were used to evaluate the impact of diazepam on larval development. Diazepam exerted no significant effect on larval mass, and a weak effect on length. Diazepam recovery was significantly higher from blanched larvae, suggesting that freeze-killing causes drug loss. This model system demonstrates the value to forensic entomologists of the standard technique of blanching larvae, followed by storage at -20℃ for toxicological analysis. We recommend that forensic toxicologists consider blanching to kill larvae before storage at low temperatures, at least for certain drugs. This approach offers the dual benefit of high-quality specimens for both PMI estimation and drug detection.

Development and age estimation of the intrapuparial period of Phormia regina (Diptera: Calliphoridae) for postmortem interval estimation.

Phormia regina (Meigen, 1826; Diptera: Calliphoridae) is a Holarctic species that rapidly colonizes carcasses and has been used as an indicator for determining the minimum postmortem interval. However, studies using morphological methods to estimate the intrapuparial age of P. regina are lacking. In this study, morphological changes within the puparium were observed under a stereomicroscope at 7 constant temperatures ranging from 16 °C to 34 °C. The intrapuparial period was categorized into 12 substages. Morphological indicators, including compound eyes, mouthparts, antennae, thorax, legs, wings, and abdomen, were recorded in detail. The observed morphological changes were divided into 6-10 substages, and the duration of each substage was also recorded in detail. The results of this study provide primary data for using the intrapuparial morphology of P. regina when pupae are collected at a crime scene and estimating the minimum postmortem interval.

Age estimation of Phormia regina pupae based on ATR-FTIR and chemometrics

Accurate postmortem interval estimation is vital in the investigation of homicides, suicides, and accidental deaths. It is key in narrowing suspect lists, improving crime-solving efficiency, and offering solace to bereaved families. The intra-puparial period, comprising about half of a fly’s developmental cycle, presents challenges for morphological age estimation. External changes are limited to color shifts and the appearance of respiratory horns on the puparium only within several hours after pupariation, while detailed internal development analysis often requires invasive methods like removing the puparium, which can be damaging. Additionally, these techniques usually depend on a forensic entomologist’s expertise, which lead to subjective biases. This study employed attenuated total reflection-fourier transform infrared spectroscopy, a rapid, non-destructive method for analyzing proteins, chitosan, and chitin in puparia. Data showed a consistent reduction in the concentration of the amide I band within the puparium during the intra-puparial development at five constant temperatures (19 °C, 22 °C, 25 °C, 28 °C and 31 °C). This trend in the spectral data effectively distinguishes pupae at various stages of intra-puparial development, facilitating precise age estimation, which is critical for the estimation of the minimum postmortem interval (PMImin). Finally, this work combined the total reflection-fourier transform infrared spectroscopy with chemometric analysis and successfully developed a partial least squares discriminant analysis model and a random forest model, with accuracies of 88 % and 81 %, respectively. These models enable the non-invasive age estimation of P. regina in its intra-puparial period, a stage traditionally difficult to assess morphologically, thus laying the groundwork for PMImin estimation using fly pupae.

Development of mixed linear models to analyze and describe the impact of malathion on the larval growth of Megaselia scalaris (Diptera: Phoridae) under various feeding media and environmental conditions.

Forensic entomology plays a crucial role in estimating the minimum postmortem interval through the study of insect larvae found at crime scenes. The precision of this estimation relies on various biotic and abiotic elements that simultaneously influence insect growth and development, encompassing factors such as temperature, humidity, photoperiod, diet, and the existence of xenobiotics in decomposing tissues. Despite numerous studies on the influence of these factors, including the impact of xenobiotics, there are currently no robust tools available for making corrections to this estimation considering concurrently all variables. In an attempt to propose an exploratory and descriptive statistical model to analyze the simultaneous effect and interaction of different variables on larval growth, this study aimed to compare the effect of malathion on the growth of Megaselia scalaris (Loew, 1866) (Diptera: Phoridae) raised in malathion-spiked porcine muscle, under controlled and uncontrolled temperature and humidity conditions (environmental conditions). Larvae were also reared using various growth media. A split-plot design that combined crossed and nested factors was employed; 2 linear mixed models were developed to assess the relationships between the variables. The model provides valuable insights into the complex interactions among xenobiotics, growth media, and environmental conditions in the size and development of M. scalaris.

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

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

The Influence of Substrates on Blow Fly (Diptera: Calliphoridae) Development

Blow flies (Diptera: Calliphoridae) can be used in forensic entomology to provide information, including an estimate of the time of colonization and minimum postmortem interval, based on insect development. This study examined the development of third instar Calliphora terraenovae Macquart in four substrates: pine shavings, soil, sand, and clay. Pupation time, survival to adult, and wing vein length were measured to examine the substrate influence. There was a significant difference in the time to pupation (F3,36 = 11.87, p < 0.0001) and the number of flies that eclosed (F3,36 = 4.716, p = 0.007) among the substrates. Blow flies pupated faster in pine shavings and eclosed as adult flies faster in sand than in other substrates. Adults eclosed in the sand in 21.9 days, followed by pine shavings (22.8), clay (24.2), and soil (26.6). Although overall survivorship was low (10–46%), the greatest number of flies eclosed in sand, and the fewest in clay. Understanding the factors that impact blow fly development can help forensic entomologists improve rearing protocols and apply this information to death investigations, especially in cases with buried remains.

Molecular identification and genetic variation of forensically important fly species (Order: Diptera) in Thailand using DNA barcoding

Forensic entomology plays a crucial role in criminal investigations by providing vital insights into minimum postmortem interval (PMImin) and corpse relocation by identifying insect species that colonize in decomposing remains. This study aimed to identify and analyze the genetic variation of forensically significant fly species in Thailand, using DNA barcoding of the mitochondrial cytochrome c oxidase subunit I COI gene. A total of 3,220 fly specimens were collected from 18 provinces across six regions of Thailand from October 2017 to September 2022. These specimens were classified by morphological identification into 21 species among three Dipteran families: Calliphoridae, Muscidae, and Sarcophagidae, with Chrysomya megacephala Diptera: Calliphoridae being the most abundant species. DNA barcoding confirmed the morphological identifications with 100 % accuracy, showing low intraspecific K2P distances0.0 to 1.1 %) and significant interspecific K2P distances 2.5 % to 17.2 %. A Neighbour-Joining (NJ) analysis was conducted to assess the molecular identification capabilities of the barcoding region. This analysis successfully recovered nearly all species as distinct monophyletic groups. The species groupings obtained were generally consistent with both morphological and molecular identifications. These findings underscore the effectiveness of DNA barcoding for precise species identification and contribute to a comprehensive database of forensically important flies in Thailand, thus facilitating improved forensic investigations and biodiversity studies.

Survival of Calliphora vicina (Diptera: Calliphoridae) embryos under cold temperature conditions: forensic implications.

Most blow flies (Diptera: Calliphoridae) species are sarcosaprophagous during the larval stage, primarily feeding on the soft tissues of carcasses during the early stages of decomposition, making them valuable forensic indicators for minimum post-mortem interval (minPMI) estimations. Like other insects, their developmental rates are strongly influenced by the environmental temperature. Although several studies have examined the influence of temperature on the development of different blow fly species, the impact of cold temperatures remains largely unstudied, despite its potential forensic implications. The present study investigates the effect of three cold temperatures (0, -2.5 and -5°C) on the survival of Calliphora vicina embryos of five different ages (0%, 20%, 40%, 60% and 80% of the total embryonic development) and two exposure times (6 and 24 h). Our results revealed significant differences in egg survival at the earliest embryonic stages (0% and 20% of the total embryonic development), resulting in high mortality rates. While at 20% of the total embryonic development high mortality was only observed under -5°C, at 0% of the total embryonic development high mortality rates were observed at all the temperatures tested. Although C. vicina embryos demonstrate tolerance to cold temperatures once they have completed the first 20% of the total embryonic development, potentially mitigating the impact of cold weather events, the possibility of minPMI underestimations due to the death of the first egg batches should not be disregarded. Additionally, considering that the embryonic development stages may last for several days under low temperatures, caution should be taken in the analysis of entomological evidence if a cadaver is discovered following cold weather episodes.

Variations in cuticular hydrocarbons of Calliphora vicina (Diptera: Calliphoridae) empty puparia: Insights for estimating late postmortem intervals.

Necrophagous flies, particularly blowflies, serve as vital indicators in forensic entomology and ecological studies, contributing to minimum postmortem interval estimations and environmental monitoring. The study investigates variations in the predominant cuticular hydrocarbons (CHCs) viz. n-C25, n-C27, n-C28, and n-C29 of empty puparia of Calliphora vicina Robineau-Desvoidy, 1830, (Diptera: Calliphoridae) across diverse environmental conditions, including burial, above-ground and indoor settings, over 90 days. Notable trends include a significant decrease in n-C25 concentrations in buried and above-ground conditions over time, while n-C27 concentrations decline in buried and above-ground conditions but remain stable indoors. Burial conditions show significant declines in n-C27 and n-C29 concentrations over time, indicating environmental influences. Conversely, above-ground conditions exhibit uniform declines in all hydrocarbons. Indoor conditions remain relatively stable, with weak correlations between weathering time and CHC concentrations. Additionally, machine learning techniques, specifically Extreme Gradient Boosting (XGBoost), are employed for age estimation of empty puparia, yielding accurate predictions across different outdoor and indoor conditions. These findings highlight the subtle responses of CHC profiles to environmental stimuli, underscoring the importance of considering environmental factors in forensic entomology and ecological research. The study advances the understanding of insect remnant degradation processes and their forensic implications. Furthermore, integrating machine learning with entomological expertise offers standardized methodologies for age determination, enhancing the reliability of entomological evidence in legal contexts and paving the way for future research and development.

A methodological approach to age estimation of the intra-puparial period of the forensically relevant blow fly Calliphora vicina via Fourier transform infrared spectroscopy.

Estimating the age of immature blow flies is of great importance for forensic entomology. However, no gold-standard technique for an accurate determination of the intra-puparial age has yet been established. Fourier transform infrared (FTIR) spectroscopy is a method to (bio-)chemically characterise material based on the absorbance of electromagnetic energy by functional groups of molecules. In recent years, it also has become a powerful tool in forensic and life sciences, as it is a fast and cost-effective way to characterise all kinds of material and biological traces. This study is the first to collect developmental reference data on the changes in absorption spectra during the intra-puparial period of the forensically important blow fly Calliphora vicina Robineau-Desvoidy (Diptera: Calliphoridae). Calliphora vicina was reared at constant 20°C and 25°C and specimens were killed every other day throughout their intra-puparial development. In order to investigate which part yields the highest detectable differences in absorption spectra throughout the intra-puparial development, each specimen was divided into two different subsamples: the pupal body and the former cuticle of the third instar, that is, the puparium. Absorption spectra were collected with a FTIR spectrometer coupled to an attenuated total reflection (ATR) unit. Classification accuracies of different wavenumber regions with two machine learning models, i.e., random forests (RF) and support vector machines (SVMs), were tested. The best age predictions for both temperature settings and machine learning models were obtained by using the full spectral range from 3700 to 600 cm-1. While SVMs resulted in better accuracies for C. vicina reared at 20°C, RFs performed almost as good as SVMs for data obtained from 25°C. In terms of sample type, the pupal body gave smoother spectra and usually better classification accuracies than the puparia. This study shows that FTIR spectroscopy is a promising technique in forensic entomology to support the estimation of the minimum post-mortem interval (PMImin), by estimating the age of a given insect specimen.

Unidirectional dispersal of blow fly larvae following decomposition fluids from a pig carcass

The decomposition of a body, and the associated gaseous and liquid discharges emanating from it, attract gravid female blow flies which lay their eggs in or on the body. After the eggs have hatched, the emerging larvae start feeding on the body. As decomposition progresses, the blow fly larvae often migrate away, typically in a random manner in search of favourable conditions for pupation. In this paper, we report on a rarely described phenomenon of unidirectional mass migration of blow fly larvae and postulate on the factors which may drive this process. A decomposition trial utilising a 60-kg pig carcass, deployed in the summer months in Table Mountain National Park, Cape Town, South Africa, was conducted in 2022. On the fifth day of the trial, simultaneous unidirectional mass dispersal of blow fly larvae was observed. The larvae moved downhill in a southeasterly direction, following the flow of decomposition fluids oozing out from the pig carcass. The ‘larval migration stream’ had a length of approximately 1.5 m with a width of 40 cm, tapering to 17 cm at the terminal point. The larval migration stream consisted of the larvae of Chrysomya albiceps and Chrysomya chloropyga. This study demonstrates the importance of understanding the timing and pattern of dispersal of post-feeding blow fly larvae in each geographical region. This is crucial as the minimum post-mortem interval can be miscalculated if older immature insects dispersing from the corpse are not considered and collected during crime scene investigations.

Novel use of a servosphere to study apodous insects: Investigation of blow fly post-feeding larval dispersal.

Blow flies (Diptera: Calliphoridae) are arguably the most important providers of an estimate of minimum post-mortem interval in forensic investigations. They usually undergo a post-feeding dispersal from the body. While previous studies have looked at dispersal of groups of larvae, recording the dispersal activity of individual larvae has not previously been demonstrated. A servosphere was used here to record the speed, directionality and phototaxis of individual post-feeding larvae of two species of blow fly on a smooth plastic surface over time. The servosphere rotates to compensate for the movement of an insect placed at its apex, thereby enabling its unimpeded locomotion in any direction to be studied and behavioural changes to external stimuli recorded. To our knowledge, the servosphere has not previously been used to study apodous insects. The objective of our study was to compare dispersal behaviour of Calliphora vicina Robineau-Desvoidy and Protophormia terraenovae (Robineau-Desvoidy), both common primary colonisers of human and animal cadavers, but showing different post-feeding dispersal strategies. Larvae of C. vicina generally disperse from the body while those of P. terraenovae remain on or close to the body. Our aims were to study (1) changes in dispersal speed over a 1-h period; (2) changes in dispersal speed once a day for 4 days, between the end of feeding and onset of pupariation; and (3) response of dispersing larvae to light. We demonstrated that (1) the movement of three C. vicina larvae tracked for 1 continuous hour on 1 day slowed from an average of 3 to <1.7 mms-1; (2) the average speed of 20 larvae of C. vicina (4.08 mms-1) recorded for 5 min once per day over a 4-day period between onset of dispersal and pupariation was significantly greater than that of P. terraenovae (2.36 mms-1; p < 0.0001), but that speed of both species increased slightly over the 4 days; (3) the responses of larvae of C. vicina to changes in light direction from the four cardinal directions of the compass, showed that they exhibited a strong negative phototactic response within 5 s, turning to move at approximately 180° away from the new light position. While conducted to observe larval calliphorid post-feeding behaviour, the results of this proof of concept study show that apodous insects can be studied on a servosphere to produce both qualitative and quantitative data.

Development and intrapuparial characterization of Peckia (Euboettcheria) collusor (Curran and Walley, 1934) (Diptera: Sarcophagidae) for application in forensic entomology

The family Sarcophagidae is very diverse in Brazil. Due to their living habits, they are the subject of many medical, veterinary, sanitary, and entomological studies. However, Sarcophagidae species are still poorly studied in forensic entomology, although they are frequently reported in carcasses and even human corpses. Thus, this study aims to identify and compare the developmental stages and intrapuparial morphological characteristics of Peckia (Euboettcheria) collusor to serve as an auxiliary tool in forensic entomology. The pupae collected after zero hour at 27 °C and 32 °C were sacrificed every three hours until the first 24 h and then every six hours until the emergence of the first adults, using 30 pupae each time, totaling 1560 for 27 °C and 1290 for 32 °C. The intrapuparial development time of this fly species under laboratory-controlled conditions was 288 h at 27 °C and 228 h at 32 °C. The 2820 pupae were analyzed according to temperature and classified into eight possible stages. This contributed to the selection of 16 key morphological characteristics to identify the age of the pupae. The identified intrapupal morphological characteristics have great potential to help researchers, experts, technical assistants, and forensic entomologists estimate the minimum post-mortem interval (minPMI) of cadavers.

Influence of photoperiod on the developmental times of the forensically relevant blow fly species Calliphora vicina (Diptera: Calliphoridae)

Blow flies (Diptera: Calliphoridae) are frequently used in forensic investigations due to their rapid colonization of cadavers. As with other insects, environmental temperature strongly influences their developmental rates. While published research has typically explored not only the impact of the environmental temperature, but also of other factors like tissue type and drug presence on developmental rates, the influence of photoperiod on the developmental rates of forensically relevant blow fly species has remained largely underexplored. Understanding the relationship between photoperiod and developmental times is crucial, as neglecting this aspect could compromise the accuracy of minimum post-mortem interval (minPMI) estimations. The present study investigates the impact of three photoperiod conditions (0:24, 8:16, and 12:12 light:darkness) on the developmental rates of Calliphora vicina, focusing on the duration of the different immature stages and on the total developmental time. Our results revealed significant variation in the intra-puparial stage and total development time across different photoperiods. Notably, a 12:12 photoperiod led to a significantly prolonged intra-puparial stage and total development time compared to the 0:24 photoperiod, suggesting that Calliphora vicina develops faster in total darkness. These findings highlight the importance of considering photoperiod in both laboratory rearing protocols and forensic casework to improve the accuracy and reliability of minPMI estimations. In this regard, preliminary guidelines and recommendations are provided.

Influence of Soil Type and Moisture on Pupal Development of Chrysomya rufifacies (Macquart) at Two Different Temperatures.

The present study investigates the developmental process of Chrysomya rufifacies (Macquart) pupae and their dependency on soil composition, moisture levels, and temperature changes. This research holds implications for forensic and veterinary applications, providing crucial insights for estimating minimum postmortem intervals and managing myiasis-causing flies in diverse environments. Specifically, the study explores the impact of five moisture content levels in loam and sandy soils (0%, 20%, 40%, 60%, and 80%) on the pupal development of Ch. rufifacies under two distinct constant temperature regimes (24 ± 1 °C and 30 ± 1 °C). A significant correlation was observed between soil type and temperature regarding the time required to complete the pupal stages; however, moisture had no significant impact. Larvae exhibited varying survival rates across the two temperatures and five moisture levels in the two types of soils, particularly under extremely lower moisture conditions (0%) at 30 ± 1 °C, failing to progress to the pupariation stage. Additionally, growth parameters such as pupal length and width of the fully formed puparia were significantly impacted by temperature, soil type, and moisture level. Adult head width was systematically measured across different moisture levels and soil types, revealing distinct temperature-dependent responses. Furthermore, a sex-specific analysis highlighted that female Ch. rufifacies consistently displayed larger head widths and higher emergence rates compared to their male counterparts. This research enhances our understanding of the intricate interrelationship among three environmental variables: soil type, moisture level, and temperature, elucidating their collective impact on the pupation processes of dipterans.

New developmental data for Dermestes maculatus (Coleoptera: Dermestidae) from the Yangtze River Delta region of China under different constant temperatures

Necrophagous beetles are sometimes used to estimate the minimum postmortem interval (PMImin) in the decay and remains stages of a corpse. Among these, the Dermestidae is one of the most common groups used and therefore has important research and application value. In this study, the developmental events of Dermestes maculatus de Geer, 1774, were recorded at six constant temperatures, and isomorphen diagrams were established. The thermobiological parameters were estimated using linear and non-linear models, and morphological indicators such as larval body length were measured. The results showed that the developmental duration of the whole immature stage decreased from 66.13 ± 8.58 days at 19 °C to 21.9 ± 2.01 days at 34 °C. The survival rate of the immature stages, especially the egg stage, varies greatly with temperature, with the lowest survival observed at 34 °C and the highest at 22 °C. The lower developmental threshold, the intrinsic optimum temperature, and the upper lethal developmental threshold obtained by the curvilinear Optim SSI models were 15.28 °C, 28.36 °C, and 34.03 °C, respectively. The body length, head capsule width, and pronotum width showed obvious growth patterns with larval developmental duration, which were characterized by equations and isomegalen diagrams. This study provides important basic data for the application of D. maculatus to estimate the PMImin in forensic entomology in the Yangtze River Delta region of China.

Bionomics, reproductive traits and assessment of forensic relevance of Peckia (Peckia) chrysostoma (Wiedemann, 1830) (Diptera: Sarcophagidae).

Peckia (Peckia) chrysostoma (Wiedemann, 1830) (Diptera: Sarcophagidae) is a colonizer of cadavers in the Neotropical Region. Nevertheless, data on development for the P. (P.) chrysostoma (e.g., instar duration) and behavioral strategies used by the species for locating and colonizing a corpse are scant. We aimed to explore bionomic and reproductive aspects of the flesh fly P. (P.) chrysostoma, and in this article we: (a) provide quantitative data on the life cycle of P. (P.) chrysostoma; (b) present bionomic measurements (length and weight) of larvae and pupae; (c) describe intrauterine egg and larvae development; and (d) analyze the ovo/larviposition behavior by gravid females. Females showed ovaries with discernible eggs and larvae between 8 and 10 days (x̅ = 23.3 eggs/female). This study reports the first observation of egg deposition, an atypical behavior for the species. The average development time for immature stages was 22.24h and 21.36h for 1st and 2nd respectively, and 3rd showed an average development time of 80.47h. Pupa had the longest duration (x̅ = 295.69h). A direct increase was observed in weight (P < 0.05) and length (P < 0.05) throughout time. The average survival time of males and females is approximately 30 days. This study expands the knowledge on P. (P.) chrysostoma, such as facultative ovoviviparity under laboratory conditions and the life cycle, which may benefit future studies for accuracy in entomology-based estimation of minimum post-mortem interval (min PMI).