Califorídeos (Diptera, Oestroidea) associados a cadáveres suínos em uma área de cerrado na Reserva Ecológica do Inhamum, Caxias, Maranhão, Brasil: subsídios para aplicação em processos forenses

Abstract

The objective of this study was to determine the fauna and the pattern in the temporal distribution of blow flies collected visting or reared from pig carcasses in a cerrado area at the Reserva Ecológica do Inhamum (REI), Caxias, MA. Two experiments were performed, one in the dry season (July and August of 2010) and the another in the rainy season (March and April of 2011). In each experiment three pig carcasses weighing 12 kg each were utilized. The carcasses were placed inside wire metal cages to prevent the access of large scavengers. A suspended trap was placed above each cage to capture adult blow flies that visited the pig carcass. Trays containing sawdust were placed under the cages in order to collect larvae leaving the carcass for pupation. A total of 51,234 specimens was collected. Of these, 25,093 adults were collected in the suspended traps and 26,141 adults were reared from the carcasses. The following species were identified: Chloroprocta idioidea (Robineau-Desvoidy, 1830) Chrysomya albiceps (Wiedemann, 1819), Chrysomya megacephala (Fabricius, 1794), Chrysomya rufifacies (Macquart, 1843), Cochliomyia macellaria (Fabricius, 1775), Hemilucilia benoisti Séguy, 1925, Hemilucilia segmentaria (Fabricius, 1805), Hemilucilia townsendi Shannon, 1926, Lucilia eximia (Wiedemann, 1818) and Lucilia sp1. Chrysomya rufifacies and H. townsendi are new records for Brazil. Cochliomyia macellaria and C. idioidea were the most abundant among the adults collected in traps, and C. albiceps and C. rufifacies were most abundant among reared specimens. The species of Hemilucilia were the only ones not reared from the carcasses. The mean time of decomposition of the pig carcasses was 10 days, and there was no difference between carcasses exposed in dry and rainy seasons. In adition, the duration of each decomposition stage did not vary between the two seasons. The duration of the stages was different, and the fermentation stage was the longest. Lucilia eximia, C. idioidea and C. macellaria, collected in the traps, were the pioneers in colonizing the pig carcasses, and they were found in all stages of decomposition. However, only L. eximia showed an association with the Initial stage, according to the IndVal index. The larvae of L. eximia were the first to leave the carcasses for pupation, followed by C. macellaria, C. albiceps and C. rufifacies. According to the IndVal index, the adults of H. townsendi and H. benoisti collected in the traps, were the only species that showed an association with only one stage, the Bloated stage. Chrysomya rufifacies and C. megacephala showed an association with the Black Putrefaction and Fermentation stages. The other species showed an association with four stages. With respect to species reared from carcasses, L. eximia and C. macellaria were the only ones that showed an association with the Bloat stage, and C. rufifacies and C. albiceps were the only species that had an association with the Dry Decay stage. The abundance values of L. eximia, C. idioidea, C. macellaria, C. albiceps, and C. rufifacies, collected in the traps, were different between the stages of decomposition, and the Black Putrefaction was the more attractive to these species. The abundance values of C. albiceps, C. rufifacies, and L. eximia, reared from the carcasses, were different between the stages, and the Dry Decay and Black Putrefaction stages showed the higher abundance of Chrysomya species and L. eximia, respectively. The species of L. eximia and C. idioidea, collected in the traps, and reared specimens of C. rufifacies were more abundant in the rainy season. With respect to the specimens collected in the traps, the ordination analyses showed that the community of blow flies has higher similarity between the Black Putrefaction, Fermentation and Dry Decay stages, due to higher richness and abundance values. However, with respect to the reared species, the community of the Fermentation and Dry Decay stages were the most similar. These results contribute to understanding the successional process of visitors adults and reared larvae of blow flies during the decomposition of pig carcasses in a cerrado area of the state of Maranhão.