An initial study of insect succession on pig carcasses in open pastures in the northwest of Uruguay

The impact of burnt carcass on the occurrence probability of Chrysomya albiceps and Lucilia ochricornis (Diptera: Calliphoridae) in southern Rio Grande do Sul, Brazil

We evaluated the impact of burnt carcasses on the probability of finding Chrysomya albiceps (Wiedemann, 1819) and Lucilia ochricornis (Wiedemann, 1830) (Diptera: Calliphoridae), and the time it took for them to arrive at the experimental carcasss. These species are biological indicators of the postmortem interval (PMI) in forensic scenarios. Using stillborn pig carcasses, this study analysed how different degrees of burning affect the level of attraction and colonisation by these species. Experimental models were subjected to level 2 (CG2) and 4 (CG4) burning according to the Crow-Glassman (CG) scale, ranging from fresh to skeletonization. Generalised Linear Models (GLM) with a Binomial distribution were used to evaluate the influence of decomposition time and experimental treatment on the probability of occurrence of each species. Additionally, survival analyses with the Weibull distribution were used to investigate how long it takes until the arrival of the first fly species in each experimental group. The results indicate that burning affects the probability of occurrence and colonisation time of the studied fly species. Although both species were affected by high degrees of burning, Lucilia ochricornis was more heavily affected than Chrysomya albiceps. This pattern was reflected in the time it took for the first occurrence of each fly species. In both cases, it took longer for flies to arrive at carcasses that had been more severely burnt. In the case of C. albiceps, the longest mean time until a fly was detected (Weibull, α = 79.9 h) happened in the CG4 group, followed by the CG2 group (α = 65.6 h) and the control group (α = 51.5 h). In contrast, for L. ochricornis, the longest mean first occurrence time (α = 85.4 h) was in CG2 group, followed by the Control (α = 49.1 h) and CG4 (α = 54.4 h) groups. This study emphasises the importance of considering whether or not a carcass was burnt and its degree of burning in forensic investigations, given that this variable can influence the accuracy of PMI estimation in crime scenes.

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.

New developmental data for Dermestes maculatus (Coleoptera: Dermestidae) from the Yangtze River Delta region of China under different constant temperatures

Necrophagous beetles are sometimes used to estimate the minimum postmortem interval (PMImin) in the decay and remains stages of a corpse. Among these, the Dermestidae is one of the most common groups used and therefore has important research and application value. In this study, the developmental events of Dermestes maculatus de Geer, 1774, were recorded at six constant temperatures, and isomorphen diagrams were established. The thermobiological parameters were estimated using linear and non-linear models, and morphological indicators such as larval body length were measured. The results showed that the developmental duration of the whole immature stage decreased from 66.13 ± 8.58 days at 19 °C to 21.9 ± 2.01 days at 34 °C. The survival rate of the immature stages, especially the egg stage, varies greatly with temperature, with the lowest survival observed at 34 °C and the highest at 22 °C. The lower developmental threshold, the intrinsic optimum temperature, and the upper lethal developmental threshold obtained by the curvilinear Optim SSI models were 15.28 °C, 28.36 °C, and 34.03 °C, respectively. The body length, head capsule width, and pronotum width showed obvious growth patterns with larval developmental duration, which were characterized by equations and isomegalen diagrams. This study provides important basic data for the application of D. maculatus to estimate the PMImin in forensic entomology in the Yangtze River Delta region of China.

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.

Forensically Relevant Flesh Flies (Diptera, Sarcophagidae, Sarcophaginae) of Southern Brazil

Flesh flies comprise a large fly family distributed worldwide that has great importance for forensic entomology. A robust and updated checklist of Sarcophaginae flies recorded in Southern Brazil is presented, based on material collected in the Rio Grande do Sul state and on a literature review. The forensic importance (high, moderate, or none) of the recorded flesh flies for estimating the postmortem interval (PMI) or inferring cases of neglect was determined based on their ecological habits. A total of 2,831 specimens representing 38 taxa were collected from three studies. Oxysarcodexia was the most abundant and species-rich genus in all three studies. Dexosarcophaga carvalhoi (Lopes) was registered for the first time in Southern Brazil. The checklist for Southern Brazil comprises 91 species distributed in 19 genera, with Oxysarcodexia, Peckia, and Lepidodexia representing the richest genera. Considering the importance of species for PMI estimation, 10, 42, and 39 species were classified as having high, moderate, or no forensic relevance, respectively. Moreover, five myiasis-causing sarcophagine flies recorded in Southern Brazil were considered to have the potential to reveal cases of neglect or mistreatment. This study revealed that Microcerella halli (Engel) and Peckia (Euboettcheria) australis (Townsend) are the most important species for PMI estimation in Southern Brazil, as they are often found breeding in corpses in this region.

A Preliminary Study of Necrophagous Flies (Insecta: Diptera) in the Lhasa Region (Qinghai-Tibet Plateau), China

Lhasa is located on the Qinghai-Tibet Plateau, with an altitude of 3,650 m, and a unique geography. Its climate is dry and cold all year round. Forensic entomological studies of the region are scarce. In this study, the diversity and seasonality of necrophagous flies in eight counties among Lhasa region were determined, and succession of necrophagous flies colonizing on rabbits in the Chengguan area of Lhasa was studied, so as to provide reference data for estimating postmortem interval (PMI) and location of death. In total, 22 species of necrophagous flies, belonging to six families were identified in Lhasa. Protophormia terraenovae (Robineau-Desvoidy, 1830) (Diptera: Calliphoridae) was the dominant species throughout the year, the diversity index (4.5834) indicated that the study on necrophagous flies in the Lhasa region is representative.

Body Size and Cuticular Hydrocarbons as Larval Age Indicators in the Forensic Blow Fly, Chrysomya albiceps (Diptera: Calliphoridae)

Chrysomya albiceps (Wiedemann 1819) is one of the most important insects in forensic entomology. Its larval developmental and survival rates are influenced by nutritional resources, temperature, humidity, and geographical regions. The present study investigated the possibility of relying on body size and cuticular hydrocarbon composition as indicators for age estimation of the different larval instars of C. albiceps. Larvae were maintained in standardized laboratory conditions at different experimental temperatures. All larval instars (first, second, and third) were randomly collected for measuring their body sizes and for estimating their cuticular hydrocarbons at different rearing temperatures (30, 35, 40, and 45°C) using gas chromatography-mass spectrometry (GC-MS). Results indicated that the duration of larval stage was temperature dependent as it gradually decreased on increasing the rearing temperature (30, 35, and 40°C) except 45°C at which larval development was ceased. In contrary, larval body size, in terms of length, width, and weight, was temperature dependent as it gradually increased with larval development on increasing rearing temperature except at 45°C at which larval development was ceased. The GC-MS showed a significant difference in the extracted components of cuticular hydrocarbons between different larval instars reared in the same temperature and between the same larval instar that reared at different temperatures. Furthermore, the highest and lowest amounts of cuticular hydrocarbons were detected at 35 and 40°C, respectively. Overall, larval body size and cuticular hydrocarbon components were temperature dependent within the range 30-40°C, which may suggest them as possible reliable age indicators for estimating the postmortem interval in the field of medicolegal entomology.

Temporal variability of the rove beetle (Coleoptera: Staphylinidae) community on small vertebrate carrion and its potential use for forensic entomology

Rove beetles (Coleoptera: Staphylinidae) are one of the most important colonizers of vertebrate cadavers. We have previously investigated carrion-associated rove beetle communities across various forests and demonstrated that the study regions are the main drivers of the local rove beetle species pool that is, in turn, able to colonize a carcass. Nevertheless, little is known about their temporal variation in community composition during the decomposition process. The aim of our study has been to analyze the temporal changes of the composition of the rove beetle community and to identify new, potentially useful candidate species for forensic entomological evaluations. We determined 80 rove beetle species that were attracted to 60 piglet cadavers across various forest stands in Germany. Both the abundance and the community composition changed over the decomposition process, independently of the species-specific geographical variation across study regions. In the region Schorfheide-Chorin, species from the genus Philonthus proved to be a suitable group for future forensic entomological investigations. They appeared in markedly high numbers at piglet cadavers from the bloated stage until the advanced decay stage. For the study region Schwäbische Alb, we newly describe the species Omalium septentrionis as a member of the carrion-associated rove beetle fauna. Based on the geographical variation in rove beetle community compositions, we have filtered out several species that might contribute to advances in postmortem interval estimations or other applied fields in forensic entomological contexts.