Coleoptera associated with buried carrion: potential forensic importance and seasonal composition

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.

The impact of the decomposition process of shallow graves on soil mite abundance

Burial of a cadaver results in a slower decomposition rate, due to more stable below‐ground temperatures and restricted access to necrophagous insects. In such circumstances, analysis of the soil mesofauna, with emphasis on mites (Acari) may be more valuable in time‐of‐death estimations. The production of volatile organic compounds of cadaveric decay results in changes, especially in the soil pH, which in turn would affect the abundance and diversity of the associated mites. In general, the effects of decomposition and the consequently altered pH levels on the abundance of mites in shallow graves, as well as the effects of fluctuating above‐ground environmental parameters (temperature, relative humidity, and precipitation) remain unknown. Here, we found that the decay of three pig cadavers buried in shallow graves (<30 cm below) caused a significant increase in the soil pH throughout decomposition, from neutral to alkaline. Cadaver decay attracted an abundance of mites: with 300 mites collected from the three pig cadavers compared to 129 from the control soil samples at the same depth. Mites rapidly became more abundant in cadaver‐associated soils than in control soils after the fresh stage. Increasing soil pH had a positive impact on the abundance of mites in graves and there was a significant interaction between cadaver body temperature and soil pH. Above‐ground fluctuations in temperature, relative humidity, and precipitation were found to have no significant direct effect on mite abundance in grave or control soils.

Calliphoridae (Diptera) Associated With Rattus rattus Carcasses in the Tijuca National Park, Rio de Janeiro, Brazil

Forensic entomology is a complementary tool for penal procedures, mainly on estimating postmortem interval. Study of cadaveric fauna in various environments is primary as source of information to support this science. This study collected information about the fauna of Calliphoridae associated to carcasses of Rattus rattus in the Tijuca National Park, RJ. Four collections were conducted, one for each season of 2015, exposing six carcasses at georeferenced points in each collection. The carcasses were placed 550 m from the boarder and equidistant by 100 m. Five decomposition stages were identified, and 10,559 individuals of Calliphoridae belonging to 10 species were collected. The most abundant species were Hemilucilia semidiaphana (Rondani) (Diptera: Calliphoridae) and Lucilia eximia (Wiedemann) (Diptera: Calliphoridae). L. eximia was the most abundant species during the Swelling and Black Putrefaction stages, succeeded in the next stages by two species of the genera Hemilucilia. H. semidiaphana was the dominant species in the last two stages, followed by Hemilucilia segmentaria (Fabricius) (Diptera: Calliphoridae). The genus Mesembrinella (Diptera: Calliphoridae) occurred mainly during the Black putrefaction stage. Mesembrinella bellardiana (Aldrich) was more abundant, with higher occurrence during the Black putrefaction and Dry decay stages. Mesembrinella peregrina (Aldrich) occurred in the two last stages with low abundance. Huascaromusca aeneiventris (Wiedemann) (Diptera: Calliphoridae) occurred during all the observed stages, mainly during the Butyric fermentation stage. Huascaromusca purpurata (Aldrich) (Diptera: Calliphoridae) occurred only during the Dry decay stage and in low abundance. A succession pattern in the carcasses colonization was observed, providing relevant information for the resolution of criminal investigations in this environment.

Dipterofauna Associated With Rat Carcasses in the Atlantic Forest, Southeastern Brazil

Each biome has its own fauna and intrinsic local conditions that determine the succession patterns of insects on carcasses. For this reason, regional studies are very important to forensics. This study deals with the flies that visit carcasses of Rattus rattus (L., 1758) in the Atlantic Forest remnant of Floresta da Tijuca, Rio de Janeiro, Brazil. We compare the diversity and relative abundance of fly families and species throughout the four seasons of the year and test for correlations between certain environmental variables and fly richness. In each of the four seasons, we exposed the carcasses of three rats. The carcasses were put in traps that were installed on the ground, separated by 100 m. The flies were collected from the carcasses on a daily basis, and were taken to the laboratory and kept in a climate chamber (28 °C day and 26 °C night). A total of 5,537 flies were captured, identified into 12 families: Calliphoridae (4,884 specimens), followed by Sarcophagidae, Micropezidae, Fannidae, Muscidae, Phoridae, and Neridae. Canonical correspondence and redundancy analyses of the environmental variables indicated no relationship between the seasons and fly abundance. Carcass decomposition lasted longer in the winter (12 d) than in the summer (8 d). The Margalef richness index indicated higher richness in the spring and winter, and lower richness in the summer. The Shannon-Wiener index and Simpson dominance indicated greater diversity in the spring. Diptera colonized all stages of decomposition. The families Calliphoridae and Sarcophagidae were more prevalent during the Fermentation stage. Our data have important implications for forensic entomology.

New records of forensic entomofauna in legally buried and exhumed human infants remains in Buenos Aires, Argentina

The study of carrion fauna associated with buried human corpses from a forensic perspective could provide useful information in criminal investigations. Insects and other arthropods remains sampled of 44 legally exhumed infant skeletons from La Plata (Buenos Aires, Argentina). They were identified at different taxonomic levels depending on the state of preservation. The specific diversity, abundance and frequency were analyzed and each taxon was assigned to the hypothetical colonization sequence: burial colonization, post-exhumation contamination at cemetery deposit or soil fauna. The phorid Dohrniphora sp. is mentioned for the first time in Argentina as carrion fauna of underground colonization, and the assemblage of Dohrniphora sp., Megaselia scalaris and Hydrotaea aenescens is proposed as indicator of buried cadavers. These findings provide new useful data to be applied in forensic entomology research.