Formicidae fauna in pig carcasses contaminated by insecticide: implications for forensic entomology

Abstract

Corpses in Brazil are commonly hidden in sugarcane plantations in the attempt to delay their finding and hinder the solution of the crime. On the other hand, these plantations are regularly sprayed with insecticides for pest control. Until now no study has reported the effects of insecticides on ant fauna. This study aimed to test the hypothesis that if a body hidden in a monoculture is accidentally contaminated by an insecticide, both the carcass decomposition pattern and the Formicidae fauna will be affected. To accomplish this, pig carcasses contaminated and non-contaminated were placed in a sugarcane monoculture environment and subsequently examined for data collection every 24 hours. The concentration used to contaminate the carcasses was 20 grams per liter of thiamethoxam. The decomposition patterns of contaminated carcasses were changed, in turn affecting the behavior of Formicidae fauna. A total of 5318 ants were collected, 3397 in contaminated carcasses and 1919 in non-contaminated carcasses, and 30 species of 11 genera were identified. According to the analysis, there are no differences between the composition of species between contaminated and non-contaminated carcasses, however, a significant difference was observed in the composition of species along the stages of decomposition between the two types of carcasses. Therefore, our hypothesis has been confirmed, contaminated carcasses undergo changes in their normal pattern of decomposition and the fauna of ants that act on them. As this group of insects has great importance for forensic sciences, the analysis of the experts should take these results into account.