Associational Patterns of Scavenger Beetles to Decomposition Stages

The influence of vertebrate scavengers on leakage of nutrients from carcasses

The decomposition of carcasses by scavengers and microbial decomposers is an important component of the biochemical cycle that can strongly alter the chemical composition of soils locally. Different scavenger guilds are assumed to have a different influence on the chemical elements that leak into the soil, although this assumption has not been empirically tested. Here, we experimentally determine how different guilds of vertebrate scavengers influence local nutrient dynamics. We performed a field experiment in which we systematically excluded different subsets of vertebrate scavengers from decomposing carcasses of fallow deer (Dama dama), and compared elemental concentrations in the soil beneath and in the vegetation next to the carcasses over time throughout the decomposition process. We used four exclusion treatments: excluding (1) no scavengers, thus allowing them all; (2) wild boar (Sus scrofa); (3) all mammals; and (4) all mammals and birds. We found that fluxes of several elements into the soil showed distinct peaks when all vertebrates were excluded. Especially, trace elements (Cu and Zn) seemed to be influenced by carcass decomposition. However, we found no differences in fluxes between partial exclusion treatments. Thus, vertebrate scavengers indeed reduce leakage of elements from carcasses into the soil, hence influencing local biochemical cycles, but did so independent of which vertebrate scavenger guild had access. Our results suggest that carcass-derived elements are dispersed over larger areas rather than locally leak into the soil when vertebrate scavengers dominate the decomposition process.

Research Status of Sarcosaprophagous Beetles as Forensic Indicators

In forensic entomology, research focused on sarcosaprophagous flies, but the sarcosaprophagous beetles, as important "forensic indicator species" of late-stage PMI in cadaver decomposition, received less attention. To increase attention on, and use and understanding of, sarcosaprophagous beetles in forensic entomology, this paper presents a bibliometric analysis of the available relevant literature. The occurrence frequency of beetle families and species from succession studies, actual cases, and experiments were calculated and illustrated using graphs. As a result, a total of 14 families and 1077 species associated with carcasses were collected, with Staphylinidae being the most frequently recorded among the families, and Necrobia rufipes (Fabricius, 1781) (Coleoptera: Cleridae) being the most frequently recorded species. In addition, a brief introduction of the cadaver-related beetles of each family is given, and research on the species identification of the immature stages, age estimation of the immature stages, and estimation of the arrival time of sarcosaprophagous beetles are discussed and prospected. This work will aid in the increased use of sarcosaprophagous beetles in forensic science practice in the future.

Beetles associated with buried carcasses: potential forensic importance in Riyadh, Saudi Arabia

Burial has a special influence on carrion fauna, which may change the rate of decomposition and so affect postmortem estimates. This study aimed to identify species and succession of beetles on buried remains. From 28 January to 31 May 2021, we examined the Coleoptera on buried and exposed rabbit carcasses, on the campus of the University of King Saud in an area measured around 175 m by 250 m. The area is almost entirely devoid of flora, except for a few acacia trees and some common wild herbs. It is about 1 km away from residential neighborhoods. In total, 165 specimens belonging to 4 families were collected. The Tenebrionidae was the most abundant family, where it formed 52% at a depth of 20 cm and 78% at a depth of 40 cm in the buried carcasses, while the family Dermestidae was the most abundant in the surface carcasses, as it formed 53% of the insects sampled. Type Mesostena puncticollis Solier, 1835 (Tenebrionidae) predominated at exposed carcasses as well as at depths of 20, 40 cm and while type Dermestes frischii Kugelann, 1792 (Dermestidae), predominated at depth of 40 cm and exposed carcasses, and type Saprinus chalcites (Illiger, 1807) (Hisiteridae) at depth of 20 only. These findings are possibly useful in forensic investigations involving buried bodies in Riyadh, Saudi Arabia.

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

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

Factors Affecting the Composition and Succession of Beetles in Exposed Pig Carcasses in Southern Brazil

Coleoptera is one of the largest taxon among animals and exhibits diverse eating habits. When associated with decaying corpses, beetles can be of great value in estimating the postmortem interval. In order to consolidate a useful database for the forensic field, it is necessary to study the entomological fauna associated with the carcasses in different geographical regions since the diversity of insects varies according to the biogeoclimate zone. Thus, this study aimed to assess the influence of environmental and ecological factors on the composition and succession of beetles associated with pig carcasses exposed in southern Brazil. Collections were carried out during the hot/dry and cold/wet seasons. A total of 415 specimens belonging to 18 Coleoptera families were sampled. The highest total abundance (n = 329) and diversity (n = 44 taxa) were recorded in the cold/wet season, corresponding to approximately 80% of the total sampled from the two seasons. Dermestidae (26.7%) was the family most abundantly sampled. Regarding eating habits, in an increasing order of importance were necrophagous (43.3%), predator (31.6%), and omnivorous (0.05%). In the hot/dry season, there was no faunal succession. In the cold/wet season, the succession was more associated with differences in abundance than to the presence or absence of a specific taxon by decomposition stage. Considering all the factors analyzed in the current study, three species of beetles, Dermestes maculatus DeGeer (Dermestidae), Euspilotus azureus (Sahlberg, 1823) (Histeridae), and Oxelytrum discicolle Brullé, 1840 (Silphidae), could be identified as being of the greatest forensic relevance in this biogeoclimatic zone.

Dermestes maculatus (Coleoptera: Dermestidae) development under fluoxetine effect using two drug administration models

Fluoxetine is a selective serotonin reuptake inhibitor, commonly used for the treatment of a variety of psychopathological conditions. As such, fluoxetine may be expected to appear in clinical and forensic cases. Dermestes maculatus De Geer (Coleoptera: Dermestidae) has been recognized as a relevant component of the insect fauna associated with decomposing human and animal remains. Experiments were conducted to study the effect of fluoxetine on developing D. maculatus using two-drug administration models: a non-living animal model (pork muscle) and a living one (Sus scrofa L. pigs). We assessed the duration of immature stages and total life cycle, as well as morphological parameters (body length, cephalic width, and weight). The effect of fluoxetine was studied at an overdose concentration: In the non-living animal model the drug was mixed with macerated pork muscle (2000 mg/kg) and in the living animal model, pigs were given the drug orally (833 mg/kg). A control was used for each model. Daily observations were performed from the beginning to the end of the experiments. GC-MS was used for drug detection and quantification. There were no statistically significant differences in the duration of immature stages, life cycle, larval mortality, morphological parameters, or sex ratio, between treatment and control, regardless of the drug administration model. Given that fluoxetine had no detectable effect on the development of D. maculatus, detection of this drug in forensic situations would not compromise the accuracy of PMI estimations.

Mites (Acari) as a Relevant Tool in Trace Evidence and Postmortem Analyses of Buried Corpses

This report interprets the presence of mite species in three clandestine graves in Europe, evaluating their potential use as trace evidence or markers. Grave 1 (Sweden): Two mite species Rhizoglyphus robini Claparède, 1869 and Parasitus loricatus (Wankel, 1861) were recovered from the surface of a body buried in a shallow grave in an area surrounded by trees, in close vicinity to house gardens. Grave 2 (Germany): Phoretic deutonymphs of Gamasodes spiniger (Trägårdh, 1910) were attached to an adult fly (Diptera: Sphaeroceridae) found within a shallow grave containing two human bodies covered in soil and dung. Grave 3 (France): P. loricatus were recovered from the soil around a body buried in a deep grave (80 cm under). In graves 1 and 3 both corpses were undergoing advanced decay and skeletization, the locations match with the subterranean habit of P. loricatus, highlighting the value of this species as a marker of graves or burials in soil and during late decomposition. R. robini is a soil mite that feeds on decayed roots and bulbs; this mite species confirms the location of the corpse within top soil, agreeing with a more specific type of superficial burial, a shallow grave. In case 2, the presence of both coprophiles, the mite G. spiniger and the carrier fly confirm association of remains with dung or animal feces. The three mite species are reported for the first time in human graves. There are no previous records of R. robini from Sweden.

Scavenging Activity of Dermestes maculatus (Coleoptera: Dermestidae) on Burned Cadaveric Tissue

The aim of this work was to study the effect that fire exposure in tissues may have on Dermestes maculatus DeGeer (Dermestidae: Dermestini) taphonomic behaviour under controlled conditions. Two different times of fire exposure (treatments) were evaluated, 15 min and 30 min, after spraying pig trotters with gasoil. The pig trotters were provided to adult hide beetles and both were maintained at 24 ± 0.1°C, 55.4% ± 2% relative humidity, and a 12:12 h day/night cycle. An unburned pig trotter was used as a control for each treatment. Observations were made and photographs were taken every 4-5 days for 4 months. Qualitative and quantitative analyses were performed. Dermestes maculatus was able to feed and reproduce on burned tissues. Beetles in adult and larvae stages produced different types of marks in several kinds of tissues such as integumental, connective, and muscular, in the controls and treatments. Apparently, 15 min of burning the pig trotters were not sufficient enough to cause differences in the taphonomic marks with respect to the control, but post mortem burning for 30 min may have implicated changes (lesser insect damage represented by lesser number and surface of both depressions and holes were found with respect to the control; greater surfaces and diameters were noticed compared to those found in the unburned pig trotters). The shape of the marks was equal in the controls and treatments.

Depressions of Dermestes maculatus (Coleoptera: Dermestidae) on Bones Could be Pupation Chambers

Dermestes maculatus DeGeer beetles feed and can leave marks on bones. This species is of medical, veterinary, and forensic importance. The aim of this work was to determine if the depressions produced on bones by these beetles could be product of pupation. We studied under controlled conditions the behavior of D. maculatus larvae maintained at 24°C ± 3°C, 52.7% average relative humidity, and a 12:12-hour light/dark cycle and fed on pig carcasses. Observations were made, and photographs were taken. The results indicated that depressions produced by D. maculatus were consequence of feeding or pupation. This is the first time that pupation chambers on bones are confirmed.

Contribution to the knowledge of Saprinus Erichson, 1834 of forensic relevance from Lebanon (Coleoptera, Histeridae)

Many histerid beetles are necrophilous on carrion during both active and advanced stages of decomposition. In this study, 13 species of Saprinus were recorded on carrion from Lebanon, containing eight that are new for the Lebanese fauna. The following Saprinus species are newly recorded from Lebanon: 1) Saprinus (S.) caerulescens caerulescens (Hoffmann, 1803); 2) S. (S.) calatravensis Fuente, 1899; 3) S. (S.) chalcites (Illiger, 1807); 4) S. (S.) godet (Brullé, 1832); 5) S. (S.) maculatus (P. Rossi, 1792); 6) S. (S.) strigil Marseul, 1855; 7) S. (S.) submarginatus J. Sahlberg, 1913; and 8) S. (S.) tenuistrius sparsutus Solsky, 1876. The peak activity was recorded, key for the species is provided, and habitus images and male genitalia are illustrated in order to facilitate their taxonomic identifications. Saprinus species are diverse and common on animal carcass; they were likewise collected from a human cadaver in Lebanon. Preliminary comments on biology and distribution of the studied species are given. Our paper represents the first faunistic study on Histeridae from Lebanon. A rigorous research program regarding the biology of Saprinus in Lebanon and the neighbouring countries would greatly improve the knowledge of the diversity, activity, and possible forensic value of Saprinus.

Active Search on Carcasses versus Pitfall Traps: a Comparison of Sampling Methods

The study of insect succession in cadavers and the classification of arthropods have mostly been done by placing a carcass in a cage, protected from vertebrate scavengers, which is then visited periodically. An alternative is to use specific traps. Few studies on carrion ecology and forensic entomology involving the carcasses of large vertebrates have employed pitfall traps. The aims of this study were to compare both sampling methods (active search on a carcass and pitfall trapping) for each coleopteran family, and to establish whether there is a discrepancy (underestimation and/or overestimation) in the presence of each family by either method. A great discrepancy was found for almost all families with some of them being more abundant in samples obtained through active search on carcasses and others in samples from traps, whereas two families did not show any bias towards a given sampling method. The fact that families may be underestimated or overestimated by the type of sampling technique highlights the importance of combining both methods, active search on carcasses and pitfall traps, in order to obtain more complete information on decomposition, carrion habitat and cadaveric families or species. Furthermore, a hypothesis advanced on the reasons for the underestimation by either sampling method showing biases towards certain families. Information about the sampling techniques indicating which would be more appropriate to detect or find a particular family is provided.