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

Forensic significance of Roundup Full® II effect on the development of Dermestes maculatus (Coleoptera: Dermestidae) and Lucilia sericata (Diptera: Calliphoridae)

The most widely used herbicides in the world are glyphosate formulations. These have been used in self-poisoning and accidental poisoning. Dermestes maculatus (Coleoptera: Dermestidae) and Lucilia sericata (Diptera: Calliphoridae) are associated with decomposing human and animal remains. The aim of the study was to evaluate Roundup Full® II effects on saprophagous insects´ development. For this, green bottle flies and hide beetles were exposed to different doses of the herbicide. The duration of life cycles was recorded by observations made every 8 and 24 h. To register possible variations in size, external morphology, and female proportion, specimens of all developmental stages were collected. The duration of developmental stages in L. sericata did not change due to the herbicide, but this reduced all size parameters of puparium with pupae inside, the weight of L1, and of adults. The larval stage and total duration in D. maculatus were decreased by the highest dose, while size parameters of hide beetles remained unchanged at all development stages. In both flies and beetles, there was no evidence of abnormal external morphology and the female proportion did not change in response to the herbicide. Finally, this study exhibited an impact on L. sericata and D. maculatus, so the possibility that the herbicide may affect other forensically important species should be considered, but more work is needed. Taxonomic determination could be done as usual; however, caution should be exercised when estimating the postmortem interval. This study represents the first to analyze a glyphosate-based herbicide associated with Forensic Entomology.

Experimental Evidence of Bone Lesions Due to Larder Beetle Dermestes maculatus (Coleoptera: Dermestidae)

Simple Summary

Larvae of the larder beetle Dermestes maculatus (Coleoptera: Dermestidae, De Geer, 1774) resemble caterpillars but actually feed on dry tissues of dead animals, and sometimes on human corpses. To hide and metamorphose into adult beetles, these larvae dig deep tunnels called pupation chambers. These holes and pits are usually observed in skins, horns, furs, or surrounding materials such as wood. They have also been reported on archaeological bones and experimentally observed on fresh pig bones, but never on humans. In this context, we investigated whether larder beetle larvae could also dig pupation chambers in human bones, and under which conditions this could occur. For this purpose, we placed medieval dry human bones as well as fresh calf and beef bones (control) with Dermestes maculatus larvae. After 1 month, we observed tunnels corresponding to pupation chambers only on dry human bones, and under conditions of high larval density. Despite these results being preliminary, they are, nonetheless, of particular interest in a forensic context, as they could help to understand taphonomic bone modifications or even the chronology of mass grave deposals.

Abstract

Dermestid beetles (Coleoptera: Dermestidae) are necrophagous insects feeding on mummified carcasses. After six to seven molts, the larvae stop feeding and dig pupation chambers to hide and safely evolve into adults. Such pupation chambers have already been observed on archaeological mammals’ bones, but the attribution and interpretation of these osteological lesions lack experimental evidence in a forensic context. To observe whether dermestid larvae dig pupation chambers in human bones, 20 or 40 Dermestes maculatus (De Geer, 1774) larvae were placed in a dermestarium with different types of bones varying in species (Bos taurus or human), age (adult or immature), and preservation method (fresh or dry). Our results show that dermestid larvae caused multiple lesions, including larval mandible traces on cortical bone, cortical perforations, drilling of pupation chambers, destruction of the trabecular network, and the perforation of cartilage. Bone destruction was mainly observed on aged dry bones, while fresh bones only exhibited soft tissue and superficial cartilage lesions. According to these results, pupation chambers could indicate the simultaneous presence of several corpses at different decomposition stages, or the addition of new corpses while others were already skeletonized. These conclusions are particularly important in the case of mass graves, where chronology is sometimes difficult to establish.

Insect Marks on Bones from La Guillerma Archaeological Locality (Salado River Depression, Buenos Aires, Argentina)

The La Guillerma archaeological locality is located in the northeast sector of Buenos Aires province (Argentina). Two of its sites (LG1 and LG5), dated between ca. 1400- and 600-years BP, have a great amount of faunal remains including deer, rodents, fish and small birds that are subjected to taphonomic agents and processes (e.g., weathering, manganese, roots). Previous studies have shown osteophagic behaviour in different insects (e.g., Coleoptera, Blattodea). In this paper, we evaluate their incidence on La Guillerma faunal assemblage. We performed an analysis on marks that were identified in bone remains of various taxa and applied the criteria for identifying bone alteration by insects (i.e., by measuring each trace and comparing them with the types of insect marks described in the literature). Fifteen specimens (LG1 = 6 and LG5 = 9) exhibited different types of modifications (e.g., pits with striae in base, pits with emanating striae, striations) that are related to the action of insects. Although the proportion of affected bones is low in relation to the total sample, we highlight our study as the first detailed analysis of insect marks on archaeological bones from Argentina. We also emphasize the significance of addressing insect-produced modifications on Argentinean archaeological sites.

Recommendations for Maintaining a Dermestid Beetle Colony (Dermestes maculatus) for Processing Human Remains

Dermestid beetles (Dermestes maculatus De Geer 1774) are small carrion insects characterized by a rounded or oval-shaped body and white abdomen with black markings. Given their natural propensity to consume soft tissue throughout various stages of decomposition, biological anthropologists have sought to use dermestids as a forensic processing method in addition to traditional chemical tissue removal techniques. Although useful, most of the existing academic literature regarding the upkeep of dermestid colonies for skeletal remains processing either lack specificity or are outdated. Additionally, nonacademic sources that contain information regarding dermestid maintenance are often disjointed, resulting in a difficulty to replicate habitat construction and ideal environmental conditions. Therefore, this technical note presents recommendations for anthropologists interested in establishing and maintaining a D. maculatus population. These recommendations are based on our experiences using several dermestid colonies to process five unembalmed human heads, procured from an anatomical gift company for a larger study on gunshot trauma. Aspects of the dermestids' environment that are crucial for the management of a healthy colony include the type of bedding, food, water, and containment method used, in addition to maintaining appropriate temperature ranges (24-27°C) and humidity levels (35-73%). Although habitat construction and dermestid maintenance involve materials that are relatively inexpensive and readily available, setting up and maintaining a D. maculatus colony can be laborious and time consuming and should only be undertaken when the volume of casework is such that this investment would be offset.

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.