The effects of insect repellent on initial Dipteran colonization of decomposing pig remains

Numerous factors influence insect colonization and development on decomposing remains and can influence postmortem interval (PMI) estimations when insects are used in investigations of suspicious deaths. This study aimed to determine whether insect repellent influences insect colonization of decomposing remains. Pig feet were divided into 4 groups: a control not sprayed with repellent, 40% DEET repellent, 98% DEET repellent, and lemon eucalyptus repellent. The feet were placed in containers, and insect visitation was observed over the course of 3 days, then insects were collected at the end of the third day. This was repeated twice a month from April through November 2022. The analysis focused on the order Diptera. Pairwise comparison determined that there was a significant delay in visitation time for remains with 98% DEET compared to remains with no repellent and 40% DEET. There were significantly fewer adult Diptera collected and more remains with no larvae or eggs present among remains treated with 98% DEET. It was concluded that low concentrations of DEET and lemon eucalyptus repellent did not delay colonization, but that high concentrations of DEET delayed visitation, reduced the number of adult flies collected from the remains, and reduced the likelihood of collecting eggs or larvae from the remains. This contributes to the understanding of factors that can influence insect colonization and development that allow for more accurate PMI estimations by suggesting that insect repellent does not need to be accounted for in PMI estimation, but a high concentration of DEET can deter insects in the short term.