Influence of the Conditions of Exposure of Pigs Carcasses (Sus scrofa domesticus L.) on the Egg-Laying Delay of Necrophagous Diptera in the Guinean Zone of Ivory Coast

摘要

A decaying cadaver is particularly attractive to necrophagous insects, more specifically Diptera. These are the first to lay their eggs on corpses. For the post mortem interval determination, the entomologist needs to know the precise time of the first egg-laying. The objective of this study is to determine the egg laying delay of these insects on a cadaver exposed in different conditions in the Guinean zone of Cote d'Ivoire. To do this, our work was been carried out in a natural environment at the National Agronomic Research Center. The experimental setup consisted of four types of wire mesh cages corresponding to the following cases: cadavers exposed to the open air or control cadavers, semi-immersed cadavers, cadavers wrapped in a shroud and suspended cadavers. Work on the site has been made from 29 October to 5 November 2019. The spawning period in species of Calliphoridae, was shorter on control and suspended cadavers. In Sarcophagidae, we noted a larviposition late on the suspended cadavers. Muscidae and Fanniidae, which intervened later on the decomposing corpses, were not observed on the suspended cadavers. These carcasses quickly dried out, no longer being able to provide nutrients essential for the proper development of larvae of species of these Diptera families. Depending on the accessibility of the corpses to necrophagous insects, the first egg-laying of Diptera were observed after 6 hours of exposure and the last after 174 hours. The exposure conditions of the corpses significantly influenced the time taken to lay the main necrophagous Diptera. As the first egg-laying of the flies occurs in the first moments after death, as long as the corpses is accessible, the results obtained during these experiments should be taken into account by the expert entomologist, in the estimation of the interval post-mortem upon discovery of a corpse.