Silphidae Research Articles

Hitchhiking mites

Phoresy is an association between two species in which one transports another. Burying beetles (Nicrophorus spp), also known as carrion beetles, carry mites. There are about 20 phoretic mites on this Nicrophorus beetle, seen in the Great Lakes–St Lawrence forest near Gravenhurst, Canada, and these mites will remain attached until they arrive at the beetle's next carcass. Male Nicrophorus beetles first locate the carcasses of small mammals or birds, and then prepare them by stripping off the fur or feathers. After locating a suitable male and mating, the female lays her eggs inside the prepared carrion. Males and females then bury the carcass in a ~20-cm-deep grave (which will become the beetle's brood chamber) by gradually excavating soil beneath it and covering it with antimicrobial secretions. Burying beetles are unusual in that both males and females take part in raising their young. The American burying beetle (Nicrophorus americanus) historically inhabited 35 states and three Canadian provinces but is now found in only five states and one province. In 1989, the US Fish and Wildlife Service listed it as endangered.

Eye-background contrast as a quantitative marker for pupal age in a forensically important carrion beetle Necrodes littoralis L. (Silphidae)

Insect pupae sampled at a death scene may be used to estimate the post-mortem interval. The pupal age is however difficult to estimate, as there are no good quantitative markers for the age of a pupa. We present a novel method for pupal age estimation based on the quantification of contrast in intensity between the eyes of a pupa and the middle grey photography card as a standard background. The intensity is measured on a standardized scale from 0 (perfect black) to 255 (perfect white) using computer graphical software and pictures of the eye and the background taken with a stereomicroscope. Eye-background contrast is calculated by subtracting the average intensity of the eye from the average intensity of the background. The method was developed and validated using pupae of Necrodes littoralis (Linnaeus, 1758) (Coleoptera: Silphidae), one of the most abundant beetle species on human cadavers in Central Europe. To develop the model, pupae were reared in 17, 20 and 23 °C, with a total of 120 specimens. The method was validated by three raters, using in total 182 pupae reared in 15, 17, 20, 23 and 25 °C. We found a gradual increase in eye-background contrast with pupal age. Changes followed generalized logistic function, with almost perfect fit of the model. Using our method pupal age was estimated with the average error of 8.1 accumulated degree-days (ADD). The largest error was 27.8 ADD and 95% of age estimates had errors smaller than 20 ADD. While using the method, different raters attained similar accuracy. In conclusion, we have demonstrated that eye-background contrast is a good quantitative marker for the age of N. littoralis pupae. Contrast measurements gave accurate estimates for pupal age. Our method is thus proven to be a candidate for a reliable approach to age insect pupae in forensic entomology.

Developmental Biology of Forensically Important Beetle, Necrophila (Calosilpha) brunnicollis (Coleoptera: Silphidae).

The postmortem interval (PMI) estimation, in cases where the body was discovered in an advanced stage of decomposition, is predominantly based on entomological evidence. However, very few forensically important species are sufficiently known in detail to allow a practical application. One of them is the carrion beetle, Necrophila (Calosilpha) brunnicollis (Kraatz, 1877). Its development from egg to adulthood was studied under a range of ecologically relevant constant temperatures to find parameters of thermal summation models. Developmental sexual dimorphism and the presence of developmental rate isomorphy were investigated. Herein we present the lower developmental thresholds and sum of effective temperatures for all developmental stages of N. brunnicollis (egg, first-third larval instar, postfeeding stage, and pupae). We did not find any evidence of developmental sexual dimorphism nor was the presence of developmental rate isomorphy confirmed. Our results present the first thermal summation model of the East Asian carrion beetle that can be used for the PMI estimation.

Standardized Laboratory Methodology for the Evaluation of Foraging Strategies in Necrophilous Beetles: A Case Study of Necrophila (Calosilpha) brunnicollis (Coleoptera: Silphidae).

Precise data regarding feeding habits of necrobiont species are a key element of food web and evolutionary ecology. They can also be used to assess the utility and value of those species for forensic entomology, where obligatory necrophagous species in particular are considered good bioindicators of postmortem or preappearance interval. However, the feeding habits of many species are known only from anecdotal field observations, often reduced to vaguely defined categories-predatory, necrophagous, or omnivorous. To address this issue, we designed a simple, in vitro behavioral experiment allowing the quantification of food preferences. Next, we applied it on Necrophila (Calosilpha) brunnicollis (Kraatz, 1877), which is a common carrion beetle of East Asia with unresolved food preferences. The results suggest that this species is preferentially necrophagous, thus valuable for forensic research. Importantly, however, our experimental design allowed us to reveal that it also readily feeds on larvae of Diptera, although they compose a minor proportion of its diet. This methodology can be applied to other species, and it could provide evidence for future decision making in forensic research.

Temperature stress induces mites to help their carrion beetle hosts by eliminating rival blowflies.

Ecological conditions are known to change the expression of mutualisms though the causal agents driving such changes remain poorly understood. Here we show that temperature stress modulates the harm threatened by a common enemy, and thereby induces a phoretic mite to become a protective mutualist. Our experiments focus on the interactions between the burying beetle Nicrophorus vespilloides, an associated mite species Poecilochirus carabi and their common enemy, blowflies, when all three species reproduce on the same small vertebrate carrion. We show that mites compete with beetle larvae for food in the absence of blowflies, and reduce beetle reproductive success. However, when blowflies breed on the carrion too, mites enhance beetle reproductive success by eating blowfly eggs. High densities of mites are especially effective at promoting beetle reproductive success at higher and lower natural ranges in temperature, when blowfly larvae are more potent rivals for the limited resources on the carcass.

Diversity and Seasonality of Small Carrion Beetles (Coleoptera: Leiodidae) in a Protected Cloud Forest in Western Mexico

We studied the fauna of leoidid beetles by sampling with carrion-baited traps, between June 2015 to July 2016, in an Acer (maple) dominated cloud forest at Talpa de Allende, Jalisco, Mexico. We collected 1,423 individuals comprising 12 species in 5 genera with the most diversity occurring in the month of July (rainy season). Dissochaetus costaricensis Salgado-Costas was the species with the highest incidence and abundance throughout the sampling. The species D. cristobalensis Peck and Cook, D. lobatus Peck and Cook, and D. ocozocoautla Peck and Cook are all new records for the state of Jalisco. We collected four additional species in the genus Dissochaetus. We consider the collection of specimens in the fungus feeding Leiodine genera Anisotoma, Colenis and Platyhydnobius incidental occurrences.

Estimation of physiological age at emergence based on traits of the forensically useful adult carrion beetle Necrodes littoralis L. (Silphidae)

The main entomological method for post-mortem interval involves estimation of age for immature insects found on a cadaver. Forensic entomologists frequently use the thermal summation value for the total immature development (K), which is a measure of physiological time needed to complete development of a species (age at emergence). K is highly variable within the species. Its true value for an adult insect may be estimated based on insect traits such as size and sex at maturity. Here, we have tested, if size and sex of adult beetles of Necrodes littoralis may be useful for the estimation of the true K. Necrodes littoralis is a Palearctic carrion beetle that frequently colonizes human cadavers in forest and agricultural environments.General and sex-specific thermal summation models for the emergence and models for the relationship between size of adult beetles and their age at emergence were developed for N. littoralis. The models were subsequently tested in the validation study. The general K for N. littoralis was about 469 (+/-25 SE) accumulated degree-days above the developmental threshold of about 8.5 (+/-0.45 SE) °C. Thermal summation parameters of the sex-specific models revealed minor differences compared to the general model. A true K was negatively related to the beetle size. Methods for the estimation of K represented its true value with different accuracy. The highest accuracy was obtained when K was estimated using beetle weight as a predictor variable and the sex-specific models for the relationship between K and size, although sex contributed slightly to this improvement. Using this method the estimated K represented the true K with the error of 6.3%, while the error for K from the general thermal summation model was about 9.7%.In conclusion, the findings demonstrate that physiological age at emergence of N. littoralis may be accurately predicted based on the adult beetle size. Necrodes littoralis is a second beetle species in which the age at maturity was more accurately represented by size-based estimates of K than K from the general thermal summation model. Therefore, we encourage testing the relationship between K and size in all insect species that are used in forensic entomology; particularly blow flies and flesh flies.

The complete mitochondrial genome of a potentially forensic related carrion beetle, Diamesus osculans (Vigors, 1825)

Diamesus osculans (Vigors, 1825) is a large size carrion beetle found on decaying corpse. Considering its potentially forensic value, the complete mitogenome of D. osculans was reported in present study. The mitogenome was assembled to 19398 base pairs in length. The composition of mitogenome is 39.45% for A, 9.64% for G, 35.43% for T and 15.48% for C. A total of 22 tRNA, 2 rRNA and 13 protein-coding genes (PCGs) were annotated. 21 tRNAs sequences could folded into the typical structure of clover-leaf, not including tRNA-Ser (AGN). A phylogenetic tree was finally constructed based on D. osculans and other species of Coleoptera.

Patterns and mechanisms for larval aggregation in carrion beetle Necrodes littoralis (Coleoptera: Silphidae)

Carrion is a patchy, nutrient-rich and frequently bulky resource that hosts a complex community of competing organisms. Several insect species have specialized to use carrion for breeding, revealing a specific suite of behavioural adaptations. Larvae of carrion insects regularly aggregate while feeding, frequently forming spectacular larval masses. Here we analysed patterns and mechanisms of collective feeding by larvae of the communally breeding carrion beetle Necrodes littoralis. Using results of laboratory behavioural assays and findings from previous field experiments using pig carcasses we found that: (1) under field conditions N. littoralis larval aggregations were prevalent on large carcasses, during late decomposition stages; (2) under laboratory conditions larvae of all instars, when present on meat, formed stable aggregations; (3) larvae consistently responded to thermal characteristics of a feeding environment, aggregating in the hottest place and following changes in the heat source location, which suggests thermal cues are important for their aggregation; and (4) ground-deposited chemical cues elicited a minor response by the third-instar larvae, which indicates these cues are less important for the aggregation of larval N. littoralis. These findings highlight the prevalence of communal feeding among necrophagous insect larvae, revealing the interspecific and intraspecific diversity of patterns and mechanisms for larval aggregation on carrion.

The carrion beetle Oxelytrum discicolle (Coleoptera: Silphidae) and the estimative of the minimum post-mortem interval in a forensic case in Brasília, Brazil

Abstract The order Coleoptera is considered second highest in forensic importance in criminal cases involving violent death, because members of this order increase in richness and abundance as the decomposition process progresses. We present here the first Forensic Entomology (FE) case in Brazil where the carrion beetle, Oxelytrum discicolle (Coleoptera: Silphidae), was used to estimate the minimum post-mortem interval (m-PMI) in a forensic case. A female corpse, at an advanced stage of decomposition, was found on a deserted highway near Brasilia/Brazil. The corpse was removed from the site, and insect samples were collected on and inside the corpse at the Forensic Medicine Institute of the Federal Police, following the specific FE protocols. The m-PMI was estimated considering two techniques, the pre-appearance interval (PAI) and the accumulated degree-days (ADD). The development stage of the larvae of O. discicolle allowed investigators to propose that this species was part of an earlier colonization, soon after death, with total length and prothorax width compatible with third instar larvae. Adult females of O. discicolle oviposited on the corpse at least 20 days before it was removed from the site where it was found, thus characterizing the m-PMI. This is the first case in which information on the development of the O. discicolle was used in a criminal investigation in Brazil.

Irish carrion beetles (Coleoptera: Silphidae): A review of the species and their known distribution

Irish carrion beetles (Coleoptera: Silphidae): A review of the species and their known distribution

Irish carrion beetles (Coleoptera: Silphidae): A review of the species and their known distribution

Carrion beetles (Coleoptera: Silphidae) are an ecologically significant insect group that play a major role in the decomposition of dead animals in natural environments. Despite their ecological as well as forensic importance, very little is known about the status and distribution of Irish silphid species. Here we provide the first complete catalogue of the carrion beetles of Ireland, the recorded distribution of each species in the country and short accounts of other aspects of the ecology of Irish Silphidae. By studying specimens from the entomology collection held by the National Museum of Ireland, collating published records from the literature, and examining records from the National Biodiversity Data Centre (Republic of Ireland) and Centre for Environmental Data and Recording (Northern Ireland), comprehensive maps of the known Irish distribution of each species are presented for the first time. Ireland is home to 13 Silphidae species which may be considered native, including one possibly endemic subspecies (Phosphuga atrata s. subrotundata). One species which was not previously considered Irish (Nicrophorus interruptus) is now confirmed as occurring in Ireland, adding to the Irish silphid fauna. Brief accounts of the biology, ecology and possible conservation status of each Irish species are provided.

Comparison of gut microbiome from Sulawesi carrion and burying beetles (Coleoptera: Silphidae) through metagenomic analysis of 16S rRNA gene

Carrion beetle (Coleoptera: Silphidae) is one of the scavengers which obtain nutrition from carcass decomposition which supported by the microbial symbionts through the mutual symbiosis. In this study, we characterized and compared the gut microbial community from the species of Nicrophorinae (Nicrophorus distinctus Grouvelle, 1885) and Silphinae (Necrophila renatae Portevin, 1920) from Dako Mountain, Central Sulawesi using 16S metagenomic approach. A total of 661 bacterial Operational Taxonomic Units (OTUs) at the species level were obtained from the guts of Ni. distinctus and Ne. renatae. Those numbers were predominated by Firmicutes and Proteobacteria, followed by Bacteriodetes in both species. Interestingly, a high number of Lactobacillales was observed in Ni. distinctus and lower number in Clostridiales and Cardiobacteriales compared to Ne. renatae, which showed higher abundance of those classes. Both of these insect species have nearly the same microbial diversity values, even though there some lower taxa levels were found different abundance. These results suggest that the patterns of the gut microbial structure depicted their roles in certain behavior and habitat on decomposing carcasses and could be correlated to the specific level of taxa roles in nutrient processing.

Effects of industrial disturbances on biodiversity of carrion-associated beetles

Energy production systems such as nuclear reactors and coal-burning power plants produce a multitude of waste contaminants including radionuclides, trace elements, and heavy metals. Among invertebrates, much of the effort to understand the impact of these contaminants has focused in aquatic environments, while relatively less attention has been on terrestrial communities. We investigated the effects of trace element and radionuclide contamination on assemblages of beetles that are drawn to vertebrate carrion. Samples were collected from riparian sites at the Savannah River Site in South Carolina to compare trap catches (i.e., measure of relative abundance) of beetles and species diversity along a habitat gradient (0–300 m) away from an aquatic habitat and between uncontaminated and contaminated sites. We collected 17,800 carrion-associated beetles representing 112 species in nine families, which were classified as either scavenger or predatory beetles. Beetle catches and species diversity were generally higher at contaminated than uncontaminated sites. These trends were likely driven by scavenger species, which showed similar patterns between sites, whereas patterns of catches and species diversity were variable between sites for predatory beetles. Species compositions of contaminated and uncontaminated sites were generally distinct, however habitat edges appeared to substantially affect beetle assemblages. Overall, our study suggests carrion beetle assemblages are sensitive to edge effects and may exhibit variable responses to the presence of anthropogenic contaminants or disturbances associated with energy production systems. Such results reflect the inherent variability among individual beetle species, populations, and communities to local environmental conditions, and underscores the need for multi-taxa approach in environmental impact assessments.

Species Assemblage of Carrion Beetles (Coleoptera: Scarabaeidae, Silphidae, Trogidae) in Three Habitats in the Northeastern Region of Aguascalientes, Mexico

We present a study on the carrion beetles of the families Scarabaeidae, Silphidae, and Trogidae from the areas surrounding Villa Juarez, Asientos, Aguascalientes, Mexico. Four sites with three types of habitat were selected: agricultural land; riparian forest; and xerophytic scrub 1 and xerophytic scrub 2. We used NTP-80 carrion traps from October 2016 to September 2017. In total, 4,831 specimens belonging to nine species, five genera, and three families were captured. The family with the highest species richness was Silphidae (s = 4), followed by Scarabaeidae (s = 3) and Trogidae (s = 2). The most abundant family was Scarabaeidae, followed by Silphidae and Trogidae. The most abundant species were: Onthophagus knulliHowden and Cartwright, 1963 (Scarabaeidae) and Nicrophorus mexicanus Matthews, 1888 (Silphidae); those with the lowest abundance were Copris sierrensisMatthews, 1961 (Scarabaeidae) and Trox spinulosus dentibius Robinson, 1940 (Trogidae), with only one individual each. The rank-abundance curves exhibit a pattern in which O. knulli was dominant with more than 70% of total abundance in each of the three sites where it was collected. Onthophagus knulli was not found in agricultural land, thus a greater similarity in species abundance was observed. We present an annotated checklist of the species found. Species richness was lower than other studies in Mexico which can be attributed to the semi-arid region and the high degree of habitat fragmentation in the area. We provide a foundation for future ecological, biogeographical, conservation, and forensic studies. Captures of O. knulli, C. sierrensis, T. spinulosus dentibius, and Nicrophorus olidus Matthews, 1886 are new state records for Aguascalientes.

Effects of diet on female fecundity and larval development in the carrion beetle Necrophila japonica

AbstractThe carrion beetle subfamily Silphinae (Coleoptera: Silphidae) contains dominant macroinvertebrates of soil ecosystems in temperate zones. However, their feeding habits, which determine the role of each species in the ecosystem, have not been sufficiently studied. Moreover, although a diet shift from necrophagy on vertebrate carcasses to predatory feeding on invertebrates is known to occur in this subfamily, the processes and mechanisms of this shift have also been inadequately addressed. We examined female fecundity and larval development on various diets in a Silphinae species, Necrophila (Eusilpha) japonica (Motschulsky). The experimental diets included a meat diet and various invertebrate diets, which reflect the ‘ancestral’ feeding habit in Silphinae, necrophagy, and the ‘derivative’ feeding habit, predatory feeding. Female fecundity was significantly higher on the meat diet (minced beef) than on an insect larvae diet (mealworms and dipteran larvae) but did not significantly differ from that on an earthworm diet. Larval developmental performance was significantly higher on the earthworm diet than on the meat and insect larvae diets. Our results for larval development were consistent with those of previous stable isotope analyses of the same species, in which isotopic values of larval samples agree with those of hypothetical consumers that utilize earthworms. The consistency of results among different methods indicates that N. japonica larvae are most likely earthworm feeders. In contrast, our results for the female fecundity experiment differed from those of previous stable isotope analyses, in which vertebrate carcasses unlikely serve as the staple diet of adults in the field; thus, the feeding habits of N. japonica adults remain unresolved. Our observations that females and larvae performed best on the meat and earthworm diets, respectively, may indicate that, in Silphinae, the diet shift from necrophagy to predatory habits occurs earlier in larvae than in adults.

Mitochondrial sequence data indicate “Vicariance by Erosion” as a mechanism of species diversification in North American Ptomaphagus (Coleoptera, Leiodidae, Cholevinae) cave beetles

Small carrion beetles (Coleoptera: Leiodidae: Cholevinae) are members of cave communities around the world and important models for understanding the colonization of caves, adaptation to cave life, and the diversification of cave-adapted lineages. We developed a molecular phylogeny to examine the diversification of thehirtus-group of the small carrion beetle genusPtomaphagus. Thehirtus-group has no surface-dwelling members; it consists of 19 short-range endemic cave- and soil-dwelling species in the central and southeastern United States of America. Taxonomic, phylogenetic and biogeographic data were previously interpreted to suggest thehirtus-group diversified within the past 350,000 years through a series of cave colonization and speciation events related to Pleistocene climate fluctuations. However, our time-calibrated molecular phylogeny resulting from the analysis of 2,300 nucleotides from five genes across three mitochondrial regions (cox1,cytb,rrnL-trnL-nad1) for all members of the clade paints a different picture. We identify three stages of diversification in thehirtus-group: (1) ~10 million years ago (mya), the lineage that develops intoP.shapardi, a soil-dwelling species from the Ozarks, diverged from the lineage that gives rise to the 18 cave-obligate members of the group; (2) between 8.5 mya and 6 mya, seven geographically distinct lineages diverged across Kentucky, Tennessee, Alabama and Georgia; six of these lineages represent a single species today, whereas (3) the ‘South Cumberlands’ lineage in Tennessee and Alabama diversified into 12 species over the past ~6 my. While the events triggering diversification during the first two stages remain to be determined, the distributions, phylogenetic relationships and divergence times in the South Cumberlands lineage are consistent with populations being isolated by vicariant events as the southern Cumberland Plateau eroded and fragmented over millions of years.

Ecological divergence of burying beetles into the forest canopy.

Closely related species with overlapping geographic ranges encounter a significant challenge: they share many ecological traits and preferences but must partition resources to coexist. In Ontario, potentially eleven species of carrion beetles (Coleoptera: Silphidae) live together and require vertebrate carrion for reproduction. Their reliance on an ephemeral and uncommon resource that is unpredictable in space and time is thought to create intense intra- and interspecific competition. Evidence suggests that burying beetle species reduce competition by partitioning carrion for breeding across different habitats, temperatures, and seasons. Here, we test predictions of an alternative axis for partitioning carrion: vertical partitioning between the ground and forest canopy. We conducted a survey of carrion beetles from May to July 2016 at the Queen’s University Biological Station across 50 randomly generated points using baited lethal traps at zero and six metres. Ground traps yielded more species and individuals compared to those in the canopy, and the number of individuals and species caught increased through the season in both trap types. Ground and canopy traps were accurately distinguished by the presence or absence of three species: ground traps contained more Nicrophorus orbicollis and Necrophila americana, while canopy traps contained more Nicrophorus pustulatus. We trapped 253 N. pustulatus in the canopy, but only 60 on the ground. N. pustulatus is thought to be rare across its geographic range, but our results suggest it is uniquely common in canopy habitats, demonstrating a vertical partitioning of habitat and resources. Our results are consistent with N. pustulatus having diverged into canopy habitats as a strategy to coexist with closely related sympatric species when competing for similar resources. We still, however, do not know the traits that allow N. pustulatus to flourish in the canopy, exactly how N. pustulatus uses canopy resources for breeding, or the factors that restrict the expansion of other burying beetles into this habitat.

Diel Activity and Effect of Carcass Decomposition on the Attractiveness to the Forensically Important Species Oxelytrum Discicolle (Coleoptera: Silphidae)†.

Oxelytrum discicolle is a carrion beetle commonly found in the Neotropical region, mainly associated with cadavers and carcasses. Information on behavior related to the likelihood of cadaver colonization is scarce. We performed two field experiments in peri-urban forest in Brazil in order to strengthen our knowledge on O. discicolle behavior. In the first experiment, we assessed the preference for piglet carcasses at different stages of decomposition offered simultaneously in two seasons, dry and rainy, while in the second experiment we investigated the diel activity of adults. A total of 493 adults were collected in the experiments. A significantly higher abundance was detected in the rainy season. There was a marked preference for carcasses at advanced stages. Adults exhibited a typical nocturnal behavior, the number trapped at night was 17 times greater than those collected during the day. Oxelytrum discicolle is nocturnal species that prefers carcasses in advanced stage of decomposition.

Facilitation costs and benefits function simultaneously on stress gradients for animals.

Understanding the variation in species interactions along environmental stress gradients is crucial for making robust ecological predictions about community responses to changing environmental conditions. The facilitation-competition framework has provided a strong basis for predictions (e.g. the stress-gradient hypothesis, SGH), yet the mechanisms behind patterns in animal interactions on stress gradients are poorly explored in particular for mobile animals. Here, we proposed a conceptual framework modelling changes in facilitation costs and benefits along stress gradients and experimentally tested this framework by measuring fitness outcomes of benefactor-beneficiary interactions across resource quality levels. Three arthropod consumer models from a broad array of environmental conditions were used including aquatic detritivores, potato moths and rainforest carrion beetles. We detected a shift to more positive interactions at increasing levels of stress thereby supporting the application of the SGH to mobile animals. While most benefactors paid no significant cost of facilitation, an increase in potato moth beneficiary's growth at high resource stress triggered costs for benefactors. This study is the first to experimentally show that both costs and benefits function simultaneously on stress gradients for animals. The proposed conceptual framework could guide future studies examining species interaction outcomes for both animals and plants in an increasingly stressed world.