Formigas associadas a carcaças de suínos (Sus scrofa Linnaeus, 1758) e seu papel na sucessão ecológica durante o processo de decomposição

Abstract

The Forensic Entomology is applied to several legal issues as a tool in criminal investigations. Several species are associated with the decomposition process, being replaced or added on the carcass, creating an entomological succession. According to literature the groups that stand out are the Diptera, Coleoptera and Hymenoptera (wasps and ants). Although the most studied insects are the Diptera and Coleoptera, because of their already proved important role, ants are present at all stages of decomposition, and may act as predators or scavenger. Therefore, the aim of this study was to evaluate the role of ants during the process of decomposition of swine carcasses in the forest environment. The experiments were performed in two different seasons in order to assess differences in ant assemblages, their roles acting as representatives of different ecological categories, and finally its role on the process of decomposition. The group of Diptera was the first to locate the carcass, being gathered representatives of 15 families, and the group of Calliphoridae considered the most representative, with 39.55%, followed by Sarcophagidae (17.82%), Muscidae (14.33%), Fannidae (9.30%), Phoridae (5.96%), and the rest of the families representing a total of 9.76% in the hot and humid season. In the cold and dry season Calliphoridae was also the most frequent (37.41%), followed by Sarcophagidae (15.39), Muscidae (11.67%), Phoridae (10.68%), Fannidae (6.75%), Anthomyidae (4.60%), and the remaining families totaled 13.50%. Ants was the second group to locate and explore the carcasses, with 39 species of six subfamilies that visited and explored the carcasses during the whole period of the experiments. From the total amount of species, 18 were common to both the stations, 7 occurred exclusively in the hot and humid season and 14 during the dry and cold season. In the hot and humid season, 18% presented scavenger habit, 35% predator, 21% omnivore, and 26% of the total amount of species was considered adventitious. During the dry and cold season 34% of the ants showed scavenger habit, 27% predator, 23% omnivore and 16% was considered adventitious. Of these categories, both predatory and scavenger species, most significantly interfere on the decomposition time, retarding it and accelerating it, respectively. The decomposition time was significantly higher during the dry and cold season, probably because of differences of the climatic conditions that interfere on the occurrence of fauna, which acts in decomposition. Therefore, these results demonstrate that the action of ants on carcasses suffering decomposition in the forest is relevant because it may act on other groups of insects or consume it directly, in this case, causing artifacts that can change the perception of forensic examiners. In both cases, it may also significantly alter the decomposition time.