Necrophagous Insects Research Articles

Temperature Influence on Prevailing Necrophagous Diptera and Bacterial Taxa With Forensic Implications for Postmortem Interval Estimation: A Review.

The decomposition process of human (and other mammalian) remains is influenced by numerous factors such as the environmental temperature, relative humidity, precipitation, geographical location of the remains, as well as the medical conditions of and any injuries sustained by the deceased person. The decomposition process generally follows a consistent pattern (fresh, bloat, active decomposition, advanced decomposition, and dry stage). Understanding the time-span of each stage of decomposition and the influence of the biotic and abiotic factors involved is imperative when trying to estimate the time elapsed since death (postmortem interval [PMI]). Over the course of decomposition, the tissues are gradually consumed by necrophagous insects and bacteria. The environmental temperature and its variations influence how insects colonize the remains, having a significant impact on their presence and developmental cycle. Additionally, the bacterial community colonizing decomposing tissues is also greatly affected by variations in environmental temperature. Because both the rate of decomposition of human remains and the relative abundance of certain insects and bacterial species are all temperature-dependent, insect and bacterial colonization data are useful as key points for the PMI estimation. This article reviews the current literature documenting the data collected on the occurrence and development cycles of predominant necrophagous Diptera (Calliphoridae, Muscidae, Sarcophagidae) and bacterial taxa involved in the decomposition of various carcasses at different temperatures. This review will impact the forensic community by providing an overview on the temperature, insect and bacterial records for the PMI estimation, seeking to aid forensic entomologists, microbiologists, pathologists, and the legal community.

Analysis of the 13C isotope ratios of amino acids in the larvae, pupae and adult stages of Calliphora vicina blow flies and their carrion food sources.

Adult blow flies are one of the first necrophagous insects to colonize fresh carcasses. The eggs they lay hatch into larvae, which then feed on the decomposing body. Like all organisms, blow flies "are what they eat," meaning that the isotopic composition of their body tissues reflects their diet. This manuscript combines ecology witha forensic application by using isotope ratio mass spectrometry (IRMS) to understand the relationship between the δ13C of amino acids in different carrion sources and the blow fly that feed on them. We also measure the amino acid-level fractionation that occurs at each major life stage of the blow flies. Adult blow flies from a commercial strain of Calliphora vicina (Robineau-Desvoidy) (Diptera: Calliphoridae) oviposited on raw pork muscle, beef muscle, or chicken liver. Larvae, pupae, and adult blow flies from each carrion were selected for amino acid compound-specific isotope analysis. Canonical discriminant analysis showed that flies were correctly classified to specific carrion types in 100% (original rules) and 96.8% (leave-one-out cross-validation [LOOCV]) of cases. Regarding life stages, we obtained 100% and 71% of correct classification in original rules and LOOCV, respectively. The isotope ratios of most of the essential amino acids did not significantly change between life stages (at 95% CI). However, some non-essential amino acids(Ala, Ser, and Glu) and some conditionally essential amino acids (Gly and Pro) were isotopically depleted in the adult stage. Except for the essential amino acids, the amino acids in larvae and pupae were enriched in 13C, and adult blow flies were depleted in 13C relative to the carrion on which they fed. These results make it possible to exclude potential sources of carrion as larval food. Amino acid-specific IRMS could help inform entomologists whether a fly has just arrived from another location to feed on a corpse or has emerged from a pupa whose feedstock was the corpse. Such insight could enhance the significance of blow flies for post-mortem interval determinations. The analytical ability to link organisms from one trophic level to another through the use of compound-specific isotope analysis of amino acids could have wide-reaching consequences in a variety of disciplines. Graphical abstract ᅟ.

Toxicological Analysis of Insects on the Corpse: a Valuable Source of Information in Forensic Investigations

Entomotoxicology as a subset of forensic entomology can be used by analysis of carcass feeding insects to detecting of drugs or toxins, as well as the cause and manner of death in cases of ante-mortem drugs intoxication. Morphine is one of the deacetylate metabolites of heroin. The aim of this study was to determine the presence and quantity of morphine in insects on the carcass and compare them with decomposing carcass. Field of this study was in Chalabeh District and toxicological tests were carried out at the Department of Forensic Toxicology, Legal Medicine Center, Kermanshah, Iran in 2017. Morphine was inoculated into live rabbit as experimental model at concentrations of 12.5, 25, 50mg/ml, similar to those normally encountered in human overdoses, then quality and quantity of morphine were determined in insects such as Chrysomya albiceps (as the first wave of insect succession on human cadavers) fed on carcass. Quantitative assessment at larvae showed that morphine was detected in all larvae (feeding and post feeding stage) fed on tissues from carcasses administered morphine, except for post-feeding larvae from R1 which received 12.5mg/ml dosage of morphine. Necrophagous insects are an indicator on the scene of crime and a potential source of information about the antemortem situation. Detection of drug in insects which is actually a reflection of the cause of death is possible.

Insect damage in dinosaur bones from the Cerro del Pueblo Formation (Late Cretaceous, Campanian) Coahuila, Mexico

This study represents the first description and analysis of insect borings on hadrosaur bones (Dinosauria: Hadrosauridae) from the Late Campanian Cerro del Pueblo Formation (CdP) of the State of Coahuila, Mexico. Here we describe seven different trace patterns that include a new Cubiculum ichnospecies and possible termite damage. The insect bone borings include holes, notches, chambers, furrows, tunnels and rosettes. Transitional structures can also be observed in the hadrosaur bones. Comparisons of these trace morphologies with extant necrophagous insect groups suggest that the CdP borings were likely the result of dermestid beetle larvae and possible termite osteophagy on a dry hadrosaur corpse prior to burial.

Behavioural response of Lucilia sericata to a decaying body infested by necrophagous insects

AbstractNumerous insect species are necrophagous, with Dipterans and Coleopterans being the most abundant on a corpse. Whether the presence of necrophageous species on a corpse affects the attraction of adult blowflies to the corpse is sparsely studied. We test the hypothesis that Lucilia sericata can discriminate the odour of a noncolonized cadaver from the odour of a cadaver on which conspecific and/or heterospecific necrophagous insects are feeding. The volatile organic compounds are collected from decomposing rats under four modalities: (i) in the absence of insects; (ii) in the presence of L. sericata adults; (iii) in the presence of Dermestes frischii adults; (iv) and in the presence of both D. frischii adults and L. sericata adults. During a multiple‐choice bioassay, blowflies are exposed to the four odour samples, and are shown to prefer the odour of a corpse where conspecific larvae are present. We also expect blowflies to avoid cadavers on which predators where present, although L. sericata are not repulsed by the odour of a cadaver colonized by hide beetles. We then compare the average quantities of all 61 volatile molecules identified, finding that the presence of necrophagous insects impacts some of them. However, none of the volatile organic compounds previously reported in the literature as being attractive for L. sericata adults are impacted by the presence of necrophagous insects. The results of the present study suggest that blowfly larvae modify the volatilome of a corpse, enabling adults to discriminate a colonized from a noncolonized corpse.

Characterization and microbial analysis of first recorded observation of Conicera similis Haliday (Diptera: Phoridae) in forensic decomposition study in Romania

The identification of necrophagous insect diversity and dynamics has forensic significance for postmortem interval estimation specific to burial. Few studies regarding the necrophagous entomofauna from buried remains have been performed to date. In contrast to the exposed carcasses, the accessibility of soil to insects is limited due to burial depth and is dependent on soil type. This study highlights the colonization behavior of Conicera similis (Haliday 1833) (Diptera: Phoridae) during carcass decomposition, a previously unobserved taxon in Romania. Adult and larvae specimens were collected from rat (Rattus norvegicus) carcasses buried at 40 cm depth in an urban park environment in June 2016 during active decomposition and their presence and activity period was correlated with the environmental parameters variation. Bacterial diversity from C. similis female adult and larvae specimens was determined via 16S rRNA gene Illumina sequencing to further characterize these commonly encountered and forensically important necrophagous insects. This report signals the easternmost geographical location in Europe (Bucharest, Romania) of C. similis to date.

Survey of Necrophagous Insects in Forensic Autopsies Associated with Human Remains in Turkey

On human corpses and animal carcasses, predominantly Diptera (flies) and Coleoptera (beetles) are found. Determination of the insect fauna that is forensically relevant in Turkey is required for forensic investigations since such baseline data currently do not exist. The aim of this study is to identify the necrophagous specimens associated with suspicious human deaths in order to determine the fauna of Ankara and its surrounding cities and to estimate the postmortem interval by using the method of accumulated degree days and hours. Insect evidence gathered from 16 sets of human remains across Turkey from 2006 to 2013 was examined. In total, 516 samples were collected. Of that total number, 428 of them were identified as blow flies, 70 were flesh flies, 9 were filth flies, 5 were flies belonging to the Heleomyzidae, one of them was a clown beetle (Histeridae) and 3 were carrion beetles (Silphidae). This is the first comprehensive study associating human corpses with forensic entomology in Turkey.

Temperature requirements for the growth of immature stages of blowflies species, Chrysomya albiceps and Calliphora vicina, (Diptera:Calliphoridae) under laboratory conditions

BackgroundIn forensic entomology, a way to estimate Post Mortem Interval (PMI) is to use development data of the first colonizing insects on a dead body. Chrysomya albiceps and Calliphora vicina, two members of the family Calliphoridae, are the first waves of necrophagous insects that are the most entomologically important fly species because of its consistent time of arrival and colonization of the body following death. Regarding the bioclimatic, environmental conditions and difference in geographic population, it seems necessary to collect data about the forensically important species in each region. In this research, the growth rate of immature stages of C.albiceps and C.vicina was studied in controlled laboratory conditions.ResultsThe results of this study showed that with increasing temperature, the duration of development was reduced. The highest period of development, for both species, is related to pupae stage and involves about half of the entire development period. The amount of Accumulated Degree Days (ADD) for the egg stage to mature of the species C.vicina, at two temperatures of 15°C and 20°C, are calculated as 416 and 396 DD, respectively.ConclusionThis study showed, temperature had significant effects on rate of the development on Chrysomya albiceps and Calliphora vicina and the amount of heat energy needed to development for these species is specific. Actually, the relationship between the development rate and temperature was significant and dependent to species and geographical regions.

Nesting strategies and disease risk in necrophagous beetles.

While the effects of carcass decomposition on microorganisms have been demonstrated in recent years, little is known of how this impacts necrophagous insects. A common assumption is that insects that exploit carcasses are exposed to a high density of potentially harmful microorganisms, but no field data have so far validated this. Necrophagous beetles such as the Scarabaeinae have complex nesting behaviors with elaborate parental care. So here, we begin to explore whether this conjunction of life history and nesting behavior represents an adaptive response to the threat posed by microbes in these environments, mainly by entomopathogens. We evaluated the density and distribution of fungi and bacteria from soil near the carcasses, and their ability to infect and kill insects that are in contact with this soil during the decomposition process. Our data showed an increase in the density and activity of opportunistic or facultative pathogens during the apex of decomposition, when there is a predominance of necrophagous insects. Meanwhile, the survivorship of bait insects decreased when in contact with soil from this period of decomposition, indicating a potential risk of infection. However, the density and activity of these microorganisms decreased with distance from the carcass, mainly with depth, which would benefit tunneller beetles in particular. We have thus provided the first field data to show that necrophagous insects are indeed exposed to high densities of potentially harmful microorganisms. Furthermore, we propose that some parental care strategies may have arisen not only as a response to competition, but also as adaptations that reduce the risks of disease. Although we have focused on carrion feeders, we suggest that the same occurs with coprophagous beetles, as both carrion and dung are nutrient‐rich resources.

Myotropic activity and immunolocalization of selected neuropeptides of the burying beetle Nicrophorus vespilloides (Coleoptera: Silphidae).

Burying beetles (Nicrophorus sp.) are necrophagous insects with developed parental care. Genome of Nicrophorus vespilloides has been recently sequenced, which makes them interesting model organism in behavioral ecology. However, we know very little about their physiology, including the functioning of their neuroendocrine system. In this study, one of the physiological activities of proctolin, myosuppressin (Nicve-MS), myoinhibitory peptide (Trica-MIP-5) and the short neuropeptide F (Nicve-sNPF) in N. vespilloides have been investigated. The tested neuropeptides were myoactive on N. vespilloides hindgut. After application of the proctolin increased hindgut contraction frequency was observed (EC50 value was 5.47 × 10-8 mol/L). The other tested neuropeptides led to inhibition of N. vespilloides hindgut contractions (Nicve-MS: IC50 = 5.20 × 10-5 mol/L; Trica-MIP-5: IC50 = 5.95 × 10-6 mol/L; Nicve-sNPF: IC50 = 4.08 × 10-5 mol/L). Moreover, the tested neuropeptides were immunolocalized in the nervous system of N. vespilloides. Neurons containing sNPF and MIP in brain and ventral nerve cord (VNC) were identified. Proctolin-immunolabeled neurons only in VNC were observed. Moreover, MIP-immunolabeled varicosities and fibers in retrocerebral complex were observed. In addition, our results have been supplemented with alignments of amino acid sequences of these neuropeptides in beetle species. This alignment analysis clearly showed amino acid sequence similarities between neuropeptides. Moreover, this allowed to deduce amino acid sequence of N. vespilloides proctolin (RYLPTa), Nicve-MS (QDVDHVFLRFa) and six isoforms of Nicve-MIP (Nicve-MIP-1-DWNRNLHSWa; Nicve-MIP-2-AWQNLQGGWa; Nicve-MIP-3-AWQNLQGGWa; Nicve-MIP-4-AWKNLNNAGWa; Nicve-MIP-5-SEWGNFRGSWa; Nicve-MIP-6- DPAWTNLKGIWa; and Nicve-sNPF-SGRSPSLRLRFa).

Forensic Entomology:an overview

Insects are the most important, in terms of number and diversity, group of animals on the earth. Insects have colonized all the world’s environments and are associated with both human life and death. Although their economical and sanitary importance is well documented, in the past few years they have been used also in a forensic context. In forensic entomology, necrophagous insects have proved useful in; studying postmortem interval (PMI), postmortem transfer (the movement of a body from one location to another after death), presence of drugs or poisons, and in identifying the victim and/or the suspect. Many species can be used to estimate the minimum PMI (mPMI), according to the stage of cadaver decomposition, body exposure, geographical region, and season. The most important British flies of forensic interest are described.

The effect of antifreeze (ethylene glycol) on the survival and the life cycle of two species of necrophagous blowflies (Diptera: Calliphoridae)

Entomotoxicology involves the analysis of the presence and the effects of toxicological substances in necrophagous insects. Results obtained by entomotoxicological studies may assist in the investigation of both the causes and the time of death of humans and animals. Ethylene glycol (EG) is easy to purchase, sweet and extremely toxic. It may be consumed accidentally or purposefully, in an attempt to cause death for suicidal or homicidal intent. Several cases report fatalities of humans and animals. The present study is the first to examine the effects of EG on the survival, developmental rate and morphology of two blowfly species, (Diptera: Calliphoridae) typically found on corpses and carcasses: Lucilia sericata (Meigen) and L. cuprina (Wiedemann). Both species were reared on substrates (beef liver) spiked with three different concentrations of EG that could cause death in either a human or cat: 1/2LD50 (T1), LD50 (T2), 2LD50 (T3), in addition to a control treatment (C) with no EG.Results of this research show that: a) both species are unable to survive if reared on a food substrate spiked with the highest concentration of EG (T3), while lower and medium concentrations (T1, T2) affect, but not prevent, the survival and the completion of the life cycle of such species; b) adults of L. sericata eclose only in C and T1, while adults of L. cuprina in both C, T1, T2; however, c) the developmental time of both species reared in T1 and T2 is statistically slower than the control; d) the body length of the immatures of both of the species reared in T1 and T2 is statistically smaller than the control.

Effect of low temperature in the development cycle of Lucilia sericata (Meigen) (Diptera, Calliphoridae): implications for the minimum postmortem interval estimation

ABSTRACTKnowledge of necrophagous insects’ developmental data is necessary for the forensic entomologist to estimate a reliable minimum postmortem interval (PMImin). Among the most represented necrophagous species, Lucilia sericata (Diptera, Calliphoridae) is particularly interesting. It is regularly identified in samples, with a predominance in summer, and is commonly used by analysts of our entomology department (Institut de Recherche Criminelle de la Gendarmerie Nationale) to estimate the PMImin with the accumulated degree days (ADD) method. This method requires the mathematical lower thermal threshold to be known. This value dictates the quality of the applied ADD method but cannot be considered as fixed, especially when insect development occurs at temperatures close to the biological threshold. In such conditions, it is necessary to study the influence of such temperatures on development rate, as well as the consequences of estimating the period of first oviposition on cadavers, when using the ADD method. Seven replicate rearings were conducted at six different temperatures: 30 °C, 24 °C, 18 °C, 15 °C, 12 °C and 10 °C. Time of development and time of emergence were recorded. The effect of low temperature on the development cycle and the reliability of the ADD method under this entire temperature spectrum were studied using different linear regression models. Calculated durations of total insect time development and experimental rearing duration were then compared. A global linear model cannot be used on the whole temperature spectrum experienced by L. sericata without resulting in an overestimation at some temperatures. We found a combination of two linear regression models to be suitable for the estimation of the total development time, depending on the temperature experienced by L. sericata. This approach allowed us to obtain a variation lower than 2% at 12 °C and 10 °C between the calculated duration and experimental duration of development. In comparison, the results obtained with a global model show a variation higher than 3% at 12 °C and 10% at 10 °C.

Thermoregulation behavior in necrophagous dipteran larvae

The forensic entomology is the use of insects to date the death. The forensic expert assessment is based on the development of necrophagous insects which are growing on the cadaver, to calculate their age and then estimate the Post-Mortem Interval. This development depends on a number of parameters like temperature, species or behavior. The French Forensic Taphonomy unit, the only expert team on the subject in France, works on the biology, physiology and ethology of the necrophagous insects. Their works are focused on thermoregulation behavior and thermal preferendum of maggot masses, aggregation phenomenon and social interaction or on food intake. These works are particularly of interest to understand the pre-social parameters and evolution strategies. More importantly, their aim is to better understand the development of necrophagous insects and, in fine, to improve the forensic expert assessment.

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

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

Species Identification of Necrophagous Insect Eggs Based on Amino Acid Profile Differences Revealed by Direct Analysis in Real Time-High Resolution Mass Spectrometry.

The colonization of decomposing remains by necrophagous insects such as blow flies is of forensic importance because the progression through the various stages of insect development can be correlated to time of death. The ability to infer this information hinges on accurate determination of the fly species that are associated with the entomological evidence collected. This evidence can include eggs, larvae, pupae, and puparial casings. Determination of the egg's identity is particularly challenging because the eggs of multiple species are morphologically very similar. We report here that the species identity of fly eggs can be determined from their chemical fingerprint signatures acquired by direct analysis in real time high-resolution mass spectrometry (DART-HRMS). Thus, freshly laid eggs were collected and readily distinguished from multiple necrophagous fly species in the Manhattan area of New York City. These species included representatives from the blow fly family (Calliphoridae), specifically Calliphora vicina, Lucilia sericata, L. coeruleiviridis, and Phormia regina species as well as the Phoridae and Sarcophagidae families. Multivariate statistical analysis of their observed DART-HRMS spectra revealed intraspecies similarities and interspecies differences that were the basis of species differentiation. The chemical basis of discrimination was differences in amino acid profiles. This represents the first chemically based fly egg identification approach with applications to forensic entomology. The rapidity of the method makes feasible the generation of a fly egg chemical profile database against which the DART-HRMS spectra of unknown eggs can be screened to rapidly assess species identity without needing to rear the eggs to adulthood.

The Odor of Death: An Overview of Current Knowledge on Characterization and Applications

After death, the human body undergoes various processes that result in the emission of volatile organic compounds (VOCs). The interest in these VOCs has increased substantially in recent years because they are key attractants for necrophagous insects and vertebrate scavengers. Identifying cadaveric VOCs has required the effective development of analytical tools for collecting, separating, identifying, and quantifying the suite of VOCs released throughout decomposition. Analytical developments for studying cadaveric VOCs in vertebrates, ecological interactions of cadaveric VOCs with the abiotic and biotic environment, and the necessity for convergence of these two areas for the progression of future knowledge are discussed herein.

A catalogue of Coleoptera specimens with potential forensic interest in the Goulandris Natural History Museum collection

This paper presents a catalogue of the Coleoptera specimens in the Goulandris Natural History Museum collection that have potential forensic interest. Forensic entomology can help to estimate the time elapsed since death by studying the necrophagous insects collected on a cadaver and its surroundings. In this paper forty eight species (369 specimens) are listed that belong to seven families: Silphidae (3 species), Staphylinidae (6 species), Histeridae (11 species), Anobiidae (4 species), Cleridae (6 species), Dermestidae (14 species), and Nitidulidae (4 species). The aim of this paper is to present this collection and its importance for studying forensic entomology.

Family Calliphoridae: An Integral Part of Postmortem Interval Estimation

Background: The arrival and activity of family Calliphoridae on a deceased corpse indoors can aid in the quantitative measure of the Postmortem Interval. Family Calliphoridae is a group of necrophagous insects that have a proclivity for decomposing corpses and are found worldwide. Their prevalence and activity on a deceased corpse indoors makes it an integral component of estimating the postmortem interval. Methods: A literary review was performed to support the hypothesis. Case control and retrospective studies were used. Study populations were not restricted to age, sex, or geographical locations. Human studies as well as animal models, due to ethical restrictions, were examined. Results: Results showed that by paralleling known developmental timelines to Calliphoridae collected from a corpse, investigating pre-arrival interval, understanding external pressures on development, and considering postfeeding behavior can lead to PMI estimated with a higher degree of accuracy. Conclusion: To disregard the role of Calliphoridae in human decomposition is to renounce a more accurate way of estimating the postmortem interval. More studies should be performed on a variety of Calliphoridae species, pupation in human corpses, and environmental stress on blowfly development to further reduce error in calculating PMI.

The Dynamic Maggot Mass Microbiome

Necrophagous insect studies have shown that decomposing vertebrate remains are an important ephemeral resource within an ecosystem. However, the microbes (e.g., bacteria and archaea) that were a part of the once living organism and the exogenous taxa that colonize this postmortem resource remain largely underexplored. Also, it is not well understood how these two kingdoms interact to recycle decaying biomass, an important mechanistic question for ecosystem function ecology. To better understand microbial community dynamics throughout decomposition, we used swine carcasses (N = 6) as models for mammalian postmortem decomposition to characterize epinecrotic microbial communities from: the abdominal skin of replicate carcasses; the internal microbiome of individual necrophagous dipteran larvae (maggots); and the microbiome of dipteran larval masses that had colonized the carcasses. Sampling occurred every 12 h for the duration of the decomposition process. We characterized these microbial communities over time using high-throughput 16S amplicon sequencing. The relative abundance of microbial taxa changed over decomposition as well as across sampling locations, suggesting significant interactions between the environment, microbes, and insect larvae. Maggot masses were represented by multiple blow fly species in each mass: Phormia regina (Meigen), Lucilia coeruleiviridis (Macquart), and Cochliomyia macellaria(F.). Relative abundance of these species within the mass also changed as decomposition progressed, suggesting the presence of certain Calliphoridae species within a mass may be associated with temporal shifts of the microbial communities. These results provide new insight into the community ecology of carrion decomposition by providing new data on interactions of microbes and dipteran larvae over time.