Insect Evidence Research Articles

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.

Unlikely allies: Camel crickets play a role in the seed dispersal of an Asian autotrophic shrub

Societal Impact StatementDust seeds, which are minute and contain minimal energy reserves, are often associated with heterotrophy (plants that obtain carbon without photosynthesis). Consequently, previous studies have mainly focused on the relationships between dust seeds and heterotrophy. However, dust seeds are also found in green plants. This manuscript focuses on the seed ecology of the apparently autotrophic shrub Rhynchotechum discolor that produces dust seeds. Using time‐lapse photography, feeding experiments, and germination tests, we show that camel crickets effectively disperse the seeds of this autotrophic shrub. This is the first study to document insect‐mediated internal seed dispersal of an autotrophic plant in regions inhabited by terrestrial mammals, offering new insights into the evolutionary ecology of dust seeds.Summary Although angiosperms exhibit a wide range of seed sizes, the mechanisms driving these differences are poorly understood. The evolution of dust seeds, which contain minimal energy reserves, is traditionally linked to heterotrophy, in which external carbon sources are provided to the embryo or seedling. Dispersal by small animals may be another important but underexplored evolutionary driver of minute seed size. However, insect endozoochory has been documented only in the seeds of heterotrophic species and autotrophic species in New Zealand (i.e., in communities without native terrestrial mammals). Here, we investigate this seed dispersal mechanism in the Japanese shrub Rhynchotechum discolor (Gesneriaceae), which produces white berries with numerous tiny ellipsoid seeds, using time‐lapse photography, feeding experiments, and germination tests, particularly focusing on potential interactions with insect internal seed dispersers. Our time‐lapse photography indicated that camel crickets predominantly feed on fallen fruits of R. discolor. Field sampling revealed that camel crickets excreted numerous intact R. discolor seeds. Feeding experiments confirmed that some camel crickets excreted a high proportion of intact seeds, many of which successfully germinated into autotrophic seedlings. The present study provides the first evidence of insects acting as endozoochorous seed dispersers in fully autotrophic plants within regions inhabited by terrestrial mammals. Our findings suggest that orthopteran‐mediated seed dispersal is more widespread than previously thought, and that dust seeds can evolve from selective pressures beyond heterotrophy, specifically through insect‐mediated seed dispersal.

Remotely controlled smart monitoring system of hermetic paddy storage to reduce postharvest losses in Bangladesh

In Bangladesh, where agriculture forms the backbone of the economy, efficient grain storage is crucial, particularly for paddy storage. Traditional methods like gunny bags and plastic containers are common, but the recent introduction of hermetic storage technologies, such as GrainPro bags and hermetic cocoons, have significantly reduced postharvest losses paddy. However, most research focuses on oxygen (O2) and carbon dioxide (CO2) levels in those open storage systems. This study introduces an innovative, cost-effective remote monitoring system for hermetically sealed grain storage, designed using locally sourced components, including a Digital Hygrometer, WiFi Mini IP Camera, and a Remote Controller unit. Tested over a 125-day period at Advanced Storage Lab, Bangladesh Agricultural University, the system effectively monitored the internal environment of the storage units. Key findings show that the internal temperature of the storage bags varied between 16.7°C and 29.2°C, demonstrating lesser fluctuation compared to the ambient temperature range of 16.1°C to 33.5°C. The relative humidity inside the storage units remained stable between 45 % and 54 %, in contrast to the external humidity range of 45 % to 81.2 %. Additionally, using the Steffe and Singh equation, an increase of 0.512 % in Equilibrium Moisture Content (EMC) of paddy was recorded. Notably, there was no evidence of insect or mold growth after 125 days of storage. This study's remote monitoring system not only marks a significant advancement in hermetic grain storage technology but also contributes to sustainable agricultural practices. It provides a practical, real-time solution to monitor and manage key environmental parameters, ensuring the preservation of grain quality over time.

Human costal cartilage, tooth cavities, and femur nutrient canals—new niches for insects used in forensic entomology

Abstract The study aimed to analyze the entomological material collected during 13 autopsies performed on the unidentified cadavers revealed at different stages of decay in the Upper Silesia Region (Poland) over 2016–2022. During the preparation of human tissues for genetic identification, we revealed larvae, puparia, and adult insects in previously undescribed locations: costal cartilage, femur nutrient canals (foramen nutrients), and tooth cavities. The taxonomical assessment was done using morphological examination or DNA barcoding, where necessary. Based on our observations, we conclude that the apical constriction, foramen, and cavities may serve as migration paths inside teeth, and the femur nutrient canals to the bone marrow. The study also revealed that Necrobia ruficollis (Fabricius, 1775) and Pyralidae Latreille, 1802 (Phycitinae) moths can form pupal chambers inside the costal cartilage, indicating that these insects can complete their life cycle inside this cache. We believe that the newly reported locations of carrion insects in human remains may be relevant to forensic entomology, as they provide new opportunities to collect insect evidence.

Moths are less attracted to light traps than they used to be

As evidence of global insect declines continues to mount, insect conservationists are becoming increasingly interested in modeling the demographic history of at-risk species from long-term survey data. However, certain entomological survey methods may be susceptible to temporal biases that will complicate these efforts. Entomological light traps, in particular, may catch fewer insects today than they once did due solely to increases in anthropogenic light pollution. Here we investigate this possibility by comparing the demographic histories of corn earworm moths (Helicoverpa zea) estimated from pairs of blacklight and pheromone traps monitored at the same farms. We find a stark decline in blacklight trap efficacy over 25 years of monitoring in Delaware, USA, mirrored over 10 years of monitoring in New Jersey, USA. While the precise causes of this decline remain a subject for discussion, the practical consequences are clear: insect conservationists cannot fully rely on long-term trends from entomological light traps.

Improving accuracy of age estimates for insect evidence-calibration of physiological age at emergence (k) using insect size but without "k versus size" model.

Postmortem interval may be estimated based on the age of insect evidence collected on a death scene. Reference data that are used in such estimation frequently comprise thermal summation constant (i.e. k), which is equal to the insect age upon completion of immature development expressed in accumulated degree-days or degree-hours (ADD or ADH). Essentially, k is a central point of an insect group and it may poorly represent insect evidence that is near the limits of variation for the group. Accordingly, it was postulated to calibrate k for particular insect evidence and insect size and sex were found to be useful for this purpose in some of the species. However, the calibration is only possible by using the model that correlates k with insect size. Since very few such models were published, this lack of data limits the calibration of k in forensic casework. In this article, we develop a formula that is useful for the calibration of k without the use of "k versus size" model (and related datasets). The formula uses k from the general thermal summation model for a species (with its standard error), size range for the species (retrieved from entomology literature), and size measurements for particular insect evidence. The calibration of k with the formula was validated using the Creophilus maxillosus (Coleoptera: Staphylinidae) and Necrodes littoralis (Coleoptera: Silphidae) datasets. It was particularly useful while analyzing unusually small and large insects, in case of which the formula reduced the inaccuracy of k from the general model on average by ~25 ADD in C. maxillosus and ~40 ADD in N. littoralis. We discuss the limitations and prospects of the calibration protocol that employs the formula.

The Diversity of Forensic Entomofauna Associated With Decaying Chicken Liver in the Tropical Region of Kerala, India.

Forensic entomology To elucidate the time of death based on insect evidence, there are several studies on forensic entomology on life cycles, environmental factors, and feeding habitats of insects. However, there have not been any comprehensive studies on forensic entomology and its usage in forensic inquiry specific to the region, especially Kerala, India. The insect succession on decomposed animal matter plays an important role in estimating minimum postmortem intervals (mPMI). Objective The purpose of the study was tounderstand forensically important insect groups and their role in the decomposition process of dead decayingmatter. The different decomposition stages of a corpse vary in attraction to necrophagous insects and the insect fauna depending on its prevailing conditions of decay. The decomposition is highly dependent on the exposition of animal matter and abiotic and biotic factors acting on it. The main objective of the present investigation was to identify the insect fauna associated with decaying chicken liver. The study also envisages comprising the diversity and abundance of insects between two different treatments of animal matter: in contact with soil and controlled conditions in a clean basin. Method The study was conducted for 45 days (until the total decomposition of the samples in both conditions) during the pre-monsoon months of April to May2022 at Chalikadavu, Muvattupuzha, in the Ernakulam district, Kerala, India. The samples were however kept away from direct sunlight and rain to avoid the direct impact on the orienting fauna. The entomofauna found to be associated with the decaying animal matter was carefully collected from the site and stored in 70% isopropyl alcohol for preservation. The total number of insects was recorded along with the hours of maximum incidence, and samples were stored in plastic vials for further identification. Result In this study, we analyzed the activities of ants, mites, wasps, cockroaches, moths, beetles, and flies during the decomposition of decaying chicken liver. Among these insects, flies and beetles are two important arthropod communities associated with animal matter decomposition. We collected these foraging organisms for morpho-taxonomic identification. The decomposition stages among the two treatments could help to understand the variable factors in the decomposition of decaying corpse with special reference to the insect fauna acting on it. Conclusion We got 100 specimens comprising 28 species in 17 families from Blattidae, Coleoptera, Diptera, Hymenoptera, and Lepidoptera. Besides this, we identified two parasitic wasps with their host (dipteran pupa), which is helpful in postmortem interval (PMI) estimation. Our analysis showed an association between decay and the activity of carrion insects. The decomposition stages among the two treatments could help to understand the variable factors in the decomposition of a decaying corpse with special reference to the insect fauna acting upon it.

Field validation of post-mortem interval estimation based on insect development. Part 1: Accuracy gains from the laboratory rearing of insect evidence

There is a consensus that forensic methods must be valid. The high quality of the method may be fully demonstrated only through validation. Unfortunately, there are very few experimental or casework validations of entomological methods for estimating post-mortem interval (PMI). Here, we present the first part of the results from the field validation of minimum PMI (PMImin) estimates based on insect development. From eight pig carcasses (24–46.4 kg) exposed in a forest habitat of Western Poland, one every one or two months, we collected insect evidence with standard entomological techniques. Using weather station temperatures and the thermal summation method, PMImin was estimated based on insect life stages that were reared under controlled laboratory conditions. Through rearing an insect until the next developmental landmark (or until eclosion), its age at the time of collection (and eventually PMImin) may be estimated by subtracting thermal accumulation in the laboratory from the corresponding thermal constant. We hypothesized that rearing insect evidence significantly improves the accuracy of PMImin compared to the estimation based on non-reared insect evidence. The results clearly supported this hypothesis. However, the accuracy significantly increased only in the case of these insects that developed normally during rearing. When their development in the laboratory was prolonged, PMImin was significantly less accurate. For the normal development sample the accuracy improved in all species and life stages. The largest accuracy gains from rearing were recorded for Calliphora vomitoria (Diptera: Calliphoridae) and Stearibia nigriceps (Diptera: Piophilidae). Moreover, when puparia or third instar larvae were reared, gains were larger than in the case of earlier life stages. In conclusion, this study demonstrated that the method of rearing insect evidence to improve the accuracy of PMImin is valid. However, it needs to be used with caution, since substantial part of the evidence may die or slow down their development in the laboratory, which violates assumptions of the method.

Insect Utilization in Criminal Investigations: The Imperative of Forensic Entomology and its Future Future Prospects

Forensic entomology is the practice of collecting, examining, and presenting insect-related evidence to support forensic investigations. The findings from such investigations play a vital role in civil and criminal cases, including law enforcement, conflict resolution, and national security matters. These findings are recognized and accepted by various legal systems worldwide. This paper specifically delves into the criminal aspect of forensic investigations, focusing on the role of forensic entomology within the field of criminology.
 In criminal cases, particularly those involving murder, forensic investigations aim to address key questions concerning the 'when,' 'where,' and 'how' of the crime. However, when a considerable amount of time has passed since the victim's death and most other biological evidence has deteriorated or become unrecoverable, the analysis of insect evidence found on the deceased becomes a crucial method for uncovering details about the victim's demise. This is where forensic entomology takes center stage, and it serves as the primary emphasis of this paper.
 The following review encompasses a comprehensive exploration of the history, methodology, and scientific principles of forensic entomology. It discusses the utility of forensic entomology in criminal investigations, highlights landmark cases where entomological evidence played a pivotal role in solving crimes, and considers the potential for further development and expansion within this field."

Rearing the Cabbage White Butterfly (Pieris rapae) in Controlled Conditions: A Case Study with Heavy Metal Tolerance.

The cabbage white butterfly (Pieris rapae) is an important system for applied pest control research and basic research in behavioral and nutritional ecology. Cabbage whites can be easily reared in controlled conditions on an artificial diet, making them a model organism of the butterfly world. In this paper, a manipulation of heavy metal exposure is used to illustrate basic methods for rearing this species. The general protocol illustrates how butterflies can be caught in the field, induced to lay eggs in greenhouse cages, and transferred as larvae to artificial diets. The methods show how butterflies can be marked, measured, and studied for a variety of research questions. The representative results give an idea of how artificial diets that vary in components can be used to assess butterfly performance relative to a control diet. More specifically, butterflies were most tolerant to nickel and least tolerant to copper, with a tolerance of zinc somewhere in the middle. Possible explanations for these results are discussed, including nickel hyper-accumulation in some mustard host plants and recent evidence in insects that copper may be more toxic than previously appreciated. Finally, the discussion first reviews variations to the protocol and directions for troubleshooting these methods, before considering how future research might further optimize the artificial diet used in this study. Overall, by providing a detailed video overview of the rearing and measurement of cabbage whites on artificial diets, this protocol provides a resource for using this system across a wide range of studies.

Effect of Lorazepam on the Development of the Hairy Maggot Blow Fly, Chrysomya rufifacies (Macquart): Implication for Forensic Entomology.

Entomotoxicology is based on using insect evidence recovered from a dead body to find out the cause and time of the death. Drugs can accumulate in fly larvae when they ingest the flesh of deceased persons and alter the normal development of the fly causing implications in calculating postmortem intervals. Lorazepam is an antidepressant generally used to treat anxiety. Larvae of Chrysomya rufifacies were fed on the beef liver mixed with lorazepam to study the effect of lorazepam on the developmental rate of larvae and to count delay in postmortem interval. Larvae grown on the beef liver with different doses of lorazepam showed delayed development as compared to normal larvae. The life cycle durations in experimental cultures with different concentrations of lorazepam completed in 1 ppm (272.56 hrs), 2 ppm (289.23 hrs), 3 ppm (324.10 hrs), and 4 ppm (350.72 hrs), while in the control culture life cycle completed in 257.26 hrs. The length, weight, and width of the larvae treated with lorazepam were smaller than the untreated culture. Length, weight, and width decreased with increased concentration of lorazepam. This delay in development ultimately affects the postmortem interval. That is why prior knowledge of the life cycle of flies with respect to various drugs needs to be studied, and these baseline data can be used to calculate postmortem interval and cause of death.

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

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

Enhanced Mercury Accumulation in Riparian Spiders: An Evidence of Insects' Emergence Effect in Aquatic and Upland Terrestrial Crossed Habitat.

Many studies have focused on mercury (Hg) accumulation in both aquatic and terrestrial organisms, but the effects of aquatic Hg on terrestrial organisms have rarely been documented. Here we report the accumulation of Hg in two species of spiders, Argiope bruennichi, inhabiting paddy fields, and Nephila clavata, inhabiting small forests in the riparian zones of two hydroelectric reservoirs in Guiyang, southwest China. The mean concentration of total mercury (THg) was higher in N. clavata (0.38mgkg-1) than in A. bruennichi (0.20mgkg-1). The monthly average THg in N. clavata, collected consecutively from May to October, and the highest values for THg in June (1.2mgkg-1) could be related to the emergence of aquatic insects during early summer, suggesting that emerging insects play a crucial role in the accumulation of Hg in riparian spiders. The high values could also be attributable to the different times of spider sampling or individual differences.

Estimating minimum post-mortem interval in a Nigerian murder case using Chrysomya megacephala (Fabricius, 1794) (Diptera: Caliphoridae): The first use of forensic entomology

Introduction: This paper presents the first application of forensic entomology in a murder investigation in Nigeria involving the remains of a 54-years victim, on January 9th, 2019 in a shaded wooded area in advanced decomposition, with no clear indication of the time of death. Objectives: To estimate the minimum post-mortem interval of a 54-year-old corpse recovered in the advanced decomposition stage using the blowfly Chrysomya megacephala and the Advance-Degree-day (ADD) method. Results: An autopsy report revealed multiple wounds to the forehead including a bullet hole. Dead embalmed dead maggots recovered from the body were identified as C. megacephala, and an accumulated degree-day model was used to estimate the minimum post-mortem interval. The findings revealed that the recovered larvae were still within the third-instar stage and had accumulated thermal energy between 58 hours (= 1.6 days, equivalent to 38.7 ADD) and 102 hours (= 2.8 days, equivalent to 68.0 ADD), suggesting that the body may have been exposed to insect activity between January 1st and 9th January 2019 after expanding the range to cater for some uncertainties. Conclusion: In this Nigerian murder case, forensic entomology used the calliphorid species C. megacephala to estimate the minPMI to be between 2 and 9 days before the body was discovered, which translates to 1st - 9th January 2019 after consideration of some uncertainties and limitations. This confirmed the crucial role that insects play in providing valuable evidence to complement forensic pathological findings in homicides when conventional methods failed. Notwithstanding difficulties with employing insect evidence in forensic investigations in Nigeria, the application of this modern forensic technique has the potential to aid in the resolution of many unsolved murder cases and expedite the delivery of justice. The ability of law enforcement agencies in Nigeria to use the potential of insects in criminal investigations can be improved through collaborations and training with professionals from diverse professions.

Evidence of two mitochondrial lineages and genetic variability in forensically important Lucilia eximia (Diptera: Calliphoridae) in Colombia.

Lucilia eximia (Wiedemann, 1819) (Diptera: Calliphoridae) is a blowfly with medical and forensic importance that shows genetic and color variation, however, these variations have not justified the description of new species. But in forensic entomology an accurate identification of species and subpopulations is crucial. We explored the genetic variation of L. eximia from eight localities, in five natural regions in Colombia using two mitochondrial fragments, including the standard locus for insect identification COI and the Cytb-tRNA-Ser-ND1 region. We found significant differentiation at COI and Cytb-tRNA-Ser-ND1 level, characterizing two lineages and revealing a deep and significant genetic split. High values of FST and genetic distances supported the two lineages. The origin of the divergence of L. eximia remains to discover. Examining whether the lineages have diverse ecological and biological behaviors could be a significant impact on the use of L. eximia in forensic and medical science. Our results could have relevant implications for the use of post-mortem interval estimation based on insect evidence, as well as our sequences improve the database used in DNA-based methods for identifying forensically important flies.

Tree insect pests and pathogens: a global systematic review of their impacts in urban areas

Trees contribute greatly to urban environments and human well-being, yet relatively little is known about the extent to which a rising incidence of tree insect pests and pathogens may be affecting these contributions. To address this issue, we undertook a systematic review and synthesis of the diverse global empirical evidence on the impacts of urban tree insect pests and pathogens, using bibliographic databases. Following screening and appraisal of over 3000 articles from a wide range of fields, 100 studies from 28 countries, spanning 1979–2021, were conceptually sorted into a three-part framework: (1) environmental impacts, representing 95 of the studies, including those reporting on tree damage, mortality, reduced growth, and changes in tree function; (2) social impacts were reported by 35 of studies, including on aesthetics, human health, and safety hazards; and (3) economic impacts, reported in 24 of studies, including on costs of pest management, and economic losses. There has been a considerable increase in urban impact studies since 2011. Evidence gaps exist on impacts on climate-regulating capacity, including temperature regulation, water retention, soil erosion, and wind protection, but also on specific hazards, nuisances, human well-being, property damages, and hazard liabilities. As a knowledge synthesis, this article presents the best available evidence of urban tree insect / pathogen impacts to guide policy, management and further research. It will enable us to better forecast how growing threats will affect the urban forest and plan for these eventualities.

Entomotoxicology as a tool for forensic investigations

Entomotoxicology is a rapidly developing field in forensic investigations that combines the disciplines of forensic entomology and toxicology. This paper reviews the application of entomotoxicology as a tool for forensic investigations and highlights its potential in providing valuable information on the presence and effects of drugs or toxins in insects found at a crime scene. The analysis of insect evidence in forensic investigations has long been used to estimate the time of death and other important factors. However, the incorporation of toxicology into this analysis can provide critical information on the presence and effects of drugs or toxins in the body. Entomotoxicology has the potential to be a valuable tool in forensic investigations, particularly in cases involving drug-related deaths or poisonings. By studying the presence and distribution of drugs or toxins in insect tissue, entomotoxicology can provide information on the timing and pattern of drug use. The use of entomotoxicology in forensic investigations is not without challenges. Factors such as post-mortem redistribution and contamination of the crime scene can impact the reliability of the results. There is also a need for standardized protocols and validation studies to ensure the accuracy and reliability of the results.

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.

Succession patterns of sarcosaprophagous insects on pig carcasses in different months in Yangtze River Delta, China

The Yangtze River Delta is one of the most economically developed regions in China, and many cases in the area require an estimation of the postmortem interval each year. This article reports forensic entomological research conducted in this region in different months. A total of 18 domestic pigs were used to study carcass decomposition, species composition, development events, and succession patterns of insects in different months from 2015 to 2021. A total of 53 arthropod species were identified, of which 38, 40, 41, and 25 were observed in April, June, September, and November, respectively. We demonstrated that insects vary in number and species from month to month, and the same species vary in number among the different months. Larvae of Calliphoridae mainly drove the decomposition of carcasses, and the decomposition rate of carcasses varied over the months. Particularly, the decomposition rate was highest in June and September, slower in April, and slowest in November. The predominant species on the carcasses also varied from month to month; Calliphora grahami Aldrich, Chrysomya pinguis (Walker), Lucilia sericata (Meigen) (Diptera: Calliphoridae), and Hydrotaea spinigera Stein (Diptera: Muscidae) were most predominant in April; Chrysomya megacephala (F.) and Chrysomya rufifacies (Macquart) (Diptera: Calliphoridae) were most predominant in June and September; and Ca. grahami was most predominant in November. In addition, the seven dominant insect species displayed four developmental events, which could be used to determine minimum postmortem interval, including adult arrival (T1), larvae wandering (T2), pupation (T3), and eclosion (T4) time on the carcasses. Insect succession patterns on carcasses also varied across months. For example, Ch. megacephala appeared later in the composition stages and was not numerically dominant in April but appeared earlier and was dominant in June and September. The results of this study guide the use of insect evidence in different months in the Yangtze River Delta region of China for estimating the postmortem interval of carcasses.

Physiological costs of facultative endosymbionts in aphids assessed from energy metabolism

Abstract Many insect species harbour heritable bacterial endosymbionts. Some facultative endosymbionts provide benefits to their hosts under certain environmental conditions. Facultative endosymbionts are expected to impose additional energetic expenditures to their host, reducing host fitness. While there is accumulating evidence in plant sucking insects that facultative endosymbionts reduce the fitness of their host under permissive conditions, no direct energy costs associated with facultative endosymbionts have been identified. Using the standard metabolic rate (SMR) as a measure of the energy cost of self‐maintenance, we investigated whether two common facultative endosymbionts Hamiltonella defensa or Regiella insecticola increase the maintenance cost of the pea aphid Acyrthosiphon pisum which could translate into host fitness reduction (‘compensation hypothesis’). In addition, we tested if there was a link between SMR and the aphid fitness and whether it depended on endosymbiont density and aphid energetic reserves. Finally, we measured SMR at different temperatures to assess the impact of suboptimal thermal conditions on physiological cost of endosymbionts. In the presence of facultative endosymbionts, aphids expressed generally a lower fitness and a higher SMR compared to uninfected ones, in accordance with the ‘compensation hypothesis’. However, the SMR difference between infected and uninfected aphids tended to decrease with increasing temperature. Complex host genotype‐by‐symbiont genotype‐by‐temperature interactions on SMR were also revealed. Energetic budget of adult aphids appeared weakly influenced by the aphid genotype and endosymbiont species, suggesting that facultative endosymbionts primarily impact the consumption of energy resources rather than their acquisition. Density of facultative endosymbionts varied largely among aphid lines but was not associated with the fitness nor metabolic rate of aphids. This work supports the energy basis of facultative endosymbiont associated fitness costs and raises new questions about the effect of facultative endosymbionts on the energy metabolism of their host. Read the free Plain Language Summary for this article on the Journal blog.