Spatio-temporal distribution and habitat preference of necrophagous Calliphoridae based on 160 real cases from Switzerland

Death, flies and environments: Towards a qualitative assessment of insect (Diptera) colonization of human cadavers retrieved from sites of death in Brazil

Empirical data on decomposition ecology have long established blowflies (Calliphoridae) and flesh flies (Sarcophagidae) (Diptera) as the most frequent colonizers of carrion, especially at early stages of decomposition. However, the scarcity of studies based on human cadavers has hindered inferences about colonization of homicide victims in real case scenarios. We describe here a survey of insects associated with cadavers retrieved from the site of death in Northeastern Brazil, with emphasis on the association between species diversity and the surrounding environment. We examined 81 cadavers, most of which were of men and resulting from violent death. Twelve cadavers (14.8 %) contained insect larvae, which were reared in the laboratory until adult emergence and identification. Ten species of Diptera effectively colonized the cadavers; seven of Family Calliphoridae - Chrysomya albiceps (Wiedemann, 1819), Chrysomya megacephala (Fabricius, 1794), Chrysomya putoria (Wiedemann, 1830), Cochliomyia macellaria (Fabricius, 1775), Hemilucilia segmentaria (Fabricius, 1805), Lucilia cuprina (Wiedemann, 1830), Lucilia eximia (Wiedemann, 1819) and three of Family Sarcophagidae, Blaesoxipha (Gigantotheca) stallengi (Lahille, 1907), Microcerella halli (Engel, 1931) and Peckia (Sarcodexia) lambens (Wiedemann, 1830). The species C. albiceps and C. macellaria were the most frequent colonizers, while Sarcophagidae was reported in only four cases. Insects were present on cadavers found in urban (n = 8) and rural (n = 4) sites, outdoors (n = 6) and inside (n = 6) residences. Presence of larvae was more frequent in the natural orifices in the head (n = 11). Clothing did not prevent from ovi/larviposition for most species. We present the first register of B. stallengi colonizing human corpses and expand the knowledge on the geographical distribution of necrophagous insects. Our protocol may contribute to forensic entomology in areas exposed to fast decomposition, such as the Neotropical Region.

Spatio-Temporal Influence on the Distribution of Forensically Relevant Blowflies (Diptera: Calliphoridae) in Gyeongsangnam-do, South Korea

The study of blowfly (Diptera: Calliphoridae) biodiversity and distribution is crucial for forensic investigations. Abiotic and biotic factors, such as season and habitat type, have a significant impact on blowfly populations. However, only a few forensic entomology studies have been conducted in South Korea, particularly in the Gyeongsangnam-do region. To address this, an extensive year-long survey was conducted to analyze the compositions, habitat preferences, distribution, and seasonal abundance of forensically relevant blowflies in urban and forested habitats of Gyeongsangnam-do, with sampling conducted twice a month using mouse carcass-baited traps set for 48 h each time. A total of 3470 adult blowflies were recorded, encompassing five genera and 13 species, with a noted absence of specimens during the winter months. The predominant species was Lucilia porphyrina, accounting for 37.2% of the total sample, followed by Chrysomya pinguis (27.6%), Lucilia sericata (7.6%), and Lucilia illustris (7.1%). The species composition was consistent across all surveyed regions; however, seasonal variation in species diversity was evident, with a peak in spring and a decline in summer. Notably, certain species exhibited clear preferences for either urban (Calliphora calliphoroides and L. sericata) or forested habitats (L. porphyrina and Ch. pinguis). This pioneering study elucidates the diverse blowfly communities in Gyeongsangnam-do, highlighting significant seasonal and habitat-dependent variations. These findings enrich our understanding of blowfly ecology in this region, offering valuable insights for forensic applications and underscoring the necessity for ongoing entomological surveillance and research.

Geographical Distribution and Multimethod Species Identification of Forensically Important Necrophagous Flies on Hainan Island

Forensic entomology offers unique advantages for the minimum postmortem interval (PMImin) estimation of decomposed corpses in forensic investigations. Accurate species identification and up-to-date locality information are essential. Hainan Island has a tropical rainforest climate and a vast territory. In this study, the community structure of necrophagous flies on Hainan Island was investigated in detail according to geographical environment. The results showed that the dominant species included C. megacephala, S. peregrina, C. rufifacies, S. misera, H. ligurriens, S. sericea, S. cinerea, S. dux, C. pinguis, and M. domestica. Furthermore, C. rufifacies and C. villeneuvi were found only in the high-altitude areas of Wuzhi Mountain, while S. cinerea was distributed only in coastal areas; the latter is a representative species of Hainan Island and has not been reported before. Furthermore, a GenBank database of forensically important flies was established, whilst a high-resolution melt (HRM) curve analysis was applied to identify the common species of Hainan Island for the first time. This study enriches the database of forensically important flies in tropical rainforest regions.

A global perspective of forensic entomology case reports from 1935 to 2022

Forensic entomology case reports are the product of rapid development in the field, the widespread acceptance of the science and the application of forensic entomological knowledge. In this study, we retrospectively summarized information derived from 307 forensic entomology case reports from 1935 to 2022 from a global perspective. Our checklist of relevant information included insect species, specific indoor or outdoor preferences, preferred temperatures, and stages of body decomposition. Finally, a concept and calculation method for postmortem interval (PMI) estimation accuracy was proposed. There were 232 cases using insect developmental data and 28 cases using succession patterns to estimate PMI. A total of 146 species of insects were involved in the cases, of which 62.3% were Diptera and 37.7% were Coleoptera. Postmortem intervals were estimated from eggs in 4 cases, larvae in 180 cases, pupae in 45 cases, and puparia in 38 cases. The majority of cases were from June to October, and the average number of species mentioned in the cases was more at 15-30 °C. Considering the standardization of application, in the majority of cases, insect evidence was collected by other personnel and sent to forensic entomologists, there was a delay in the sampling, and the scene or meteorological data were directly used without correcting. Our data shows that there are still many shortcomings in the universality and standardization of forensic entomology in its practical application.

A synthesis of carcass decomposition studies conducted at a tropical (Aw) taphonomy facility: 2013-2022

Decomposition studies have been conducted in several regions of the world, but relatively few have investigated taphonomy in tropical environments. Even fewer have explored carcass decomposition during multiple tropical seasons, leaving the relationships between season and decomposition in tropical environments poorly understood. Ten decomposition studies using 30 carcasses were conducted in Honolulu, Hawaii, USA to start addressing this knowledge gap. These studies show that some postmortem processes were observed regardless of season. Carcass temperature and chemistry were spatiotemporally variable. Fly larval masses were consistently observed within 3 days (∼75 ADD) postmortem and carcasses lost 60%-90% of mass by 10 days (∼250 ADD) postmortem (Total Body Score ∼26). Season had a significant effect on decomposition, yet the warmest and most humid seasons did not always result in the most rapid and extensive decomposition. Seasonal variation appears to be less pronounced than at other tropical decomposition sites.

Aggregation in an heterospecific population of blowfly larvae: social behaviour is impacted by species-specific thermal requirements and settlement order

Larvae of several blowfly species grow on carcasses and actively aggregate together. They face harsh developmental conditions resulting in a strong pressure to reduce development time: this is achieved either through thermoregulation or aggregation. We investigate how these two developmental strategies are modulated within heterospecific groups. In a first experiment, larvae of two species with different thermal requirements were deposited simultaneously on a thermal gradient. This resulted in the formation of two monospecific groups, each located at the species-specific thermal preferendum. However, when Calliphora vomitoria (Linnaeus) larvae were placed first, the later arriving Lucilia sericata (Meigen) larvae attracted the whole group to its own thermal preferendum. In the reverse experiment, half of the replicates resulted in single dense heterospecific groups observed at temperatures ranging from C. vomitoria to L. sericata preferendum. The other half of the replicates resulted in loose groups spread out on the thermal gradient. These results highlight the emergence of collective decisions ranging from thermal optimization to heterospecific aggregation at suboptimal temperatures. They demonstrate that species settlement order strongly affects self-organization processes and mixed-species group formation. We conclude that thermal optimization and heterospecific niche construction are two developmental strategies of carrion fly larvae. This article is part of the theme issue 'Mixed-species groups and aggregations: shaping ecological and behavioural patterns and processes'.

Effect of diazinon (organophosphate) on the composition and succession of Calliphoridae assemblages in rabbit carcasses in the Eastern Amazon

Fatal poisonings with diazinon may occur both accidentally or intentionally in suicide cases. Forensic entomotoxicology can aid in understanding these deaths by detecting and analyzing the interference of toxic substances in the biology of necrophagous insects. Hence, this study sought to evaluate diazinon's effect on the composition and succession of calliphorid species in the tropical savannas of the Amazon. Nine rabbit carcasses were divided into three groups: one control and two diazinon treatments (100 mg/kg and 300 mg/kg); each group had three replicates. Three fragments of the Amazon tropical savanna were selected for the experiments. Daily collections of adult and immature calliphorids were performed. Five decomposition stages were observed: fresh, bloated, active decay co-occurring, advanced decay, and dry. Eight species of Calliphoridae were identified among the collected adults: Chloroprocta idioidea (0.1%), Chrysomya albiceps (58.3%), Chrysomya megacephala (14.2%), Chrysomya putoria (2.6%), Cochliomyia hominivorax (1.3%), Cochliomyia macellaria (0.5%), Lucilia eximia (19.8%), and Paralucilia paraensis (3.3%). The adult specimens in the control group with the highest abundance were observed only from the advanced decay stage onward. In the dry stage, abundance was higher in control than in treated carcasses. From the sampled 941 Calliphorid immatures, three species were identified: C. albiceps (76,3%), C. putoria (1%), and L. eximia (22,7). The number of immatures was higher in control than in treated carcasses. Therefore, diazinon interferes with the putrefaction timeframe in carcasses, slowing the decomposition stages and affecting their colonization by immature forms of Calliphoridae.

Decomposition and insect succession on human cadavers in a humid, continental (Dfb) climate (Quebec, Canada)

Forensic entomology has been developing globally for decades. Despite this discipline being used in criminal investigations around the world, only a few controlled studies have been performed on human cadavers in human decomposition facilities, with the majority of these being conducted in warm and often dry climates. Therefore, the purpose of our research was to catalogue the first published data on insects associated with decomposed human bodies in a humid, continental (Dfb) climate. Specifically, our objective was to document the diversity and succession of the entomofauna associated with human cadavers throughout the decomposition process, in the Quebec province of Canada, during the summer season. Two human cadavers were studied in 2020 at the site for Research in Experimental and Social Thanatology, REST, located in Bécancour (Quebec, Canada). Insects (and other arthropods) were regularly sampled by visual observations, collection from the cadavers, and by using an entomological net and pitfall traps. Our results highlight that the decomposition process is a heterogeneous and complex process in Quebec, with cadavers showing signs of precocious desiccation/mummification. In addition, our observations confirm that the presence of superficial skin lesions accelerates the colonization of blow flies (Diptera: Calliphoridae) and, consequently, the process of decomposition. Finally, we were able to discriminate between "early colonizers" (e.g., Calliphoridae Lucilia sp. or Calliphora livida), "late colonizers" (e.g., larvae of Piophilidae or Heleomyzidae), and "non-specific colonizers." We also officially report the first observation of Cochliomyia macellaria (Diptera: Calliphoridae) in Quebec. These findings will provide new information to help medico-legal death investigations by determining the minimum time elapsed since death and the circumstances surrounding death.

Dermestes (s.str.) haemorrhoidalis (Coleoptera: Dermestidae)-The Most Frequent Species on Mummified Human Corpses in Indoor Conditions? Three Cases from Southwestern Poland

Beetles of the family Dermestidae, especially of the genus Dermestes Linnaeus, 1758, are often identified on corpses in late stages of decomposition. They usually feed on remains devoid of organs and soft tissues or when the corpses undergo mummification. In Europe, eight species from two subgenera Dermestes and Dermestinus Zhantiev, 1967, have so far been identified on human corpses. Despite the relatively frequent presence of Dermestes sp. in experimental studies conducted in Poland, no reports concerning Dermestes directly collected from human corpses have been published to date. This article again describes observations of Dermestidae collected from human corpses found in indoor conditions in Wrocław, the capital of the Dolnośląskie Voivodeship. For the second time, there is evidence of the presence of Dermestes (s.str.) haemorrhoidalis on human corpses-a species considered to be relatively rare, as evidenced by faunistic data published from Poland, as well as the results of ongoing experiments of forensic interest.

"Salt mummification" - atypical method of embalming a corpse

It is extremely rare for table salt to be used to preserve a dead body in criminal cases. In the case presented here, after the death of his 85-year-old mother, a son kept her body preserved in table salt for about 2 years to extort social benefits (pension). Before her death, the woman had been hospitalised twice due to chronic diseases. The case has been examined by the multi-disciplinary team. The unusual conditions in which the corpse was stored influenced its good condition (close to mummification), with limited colonisation of the corpse by necrophagous insects and insects involved in soft tissue biolysis (i.e. selected Diptera or Coleoptera). The use of table salt inhibited the growth of most fungi which would normally be present on a corpse stored in ambient conditions, and the corpse's surface was colonised by halophilic fungus (Scopulariopsis brevicaulis).