Postmortem Artifacts Made by Ants and the Effect of Ant Activity on Decompositional Rates

Abstract

Ants belong to the family Formicidae of the order Hymenoptera and they are one of the world's dominant insect groups. Ants can be present at all stages of carrion decomposition as they are typically observed shortly after death or during the early postmortem period, but even later once the fly maggots had left the body. Their role in the faunal succession varies from predator on the eggs and larvae of other insects (mainly Diptera), thus reducing significantly the rate of decomposition, to scavenger on the flesh or exudates from the corpse itself. As they can deeply affect the occurrence of cadaver entomofauna, the presence or absence of ants should be taken into account in every case involving postmortem interval estimates based on entomological evidence. In fact, the effects of ants on carrion reduction seem to be mainly dependent on species, on their amount or abundance, and on geographic area. The feeding action of ants can cause many irregular, serpiginous, scalloped areas of superficial skin loss, and small punctate and scratch-type lesions may be often observed on the body, which are the result of postmortem ant bites. Usually ant injuries are orange-pink to yellow in color and diffusely scattered over the skin surface. These injuries consist of small and rather shallow gnawed holes that can be easily misinterpreted as antemortem abrasions or resulting from strong acids. No bleeding is associated with such skin lesions but sometimes considerable hemorrhage can take place, especially where removal of superficial layers of skin occurs in congested parts of the body. As ants attack the uncovered areas of the body, ant bites can frequently give rise to suspicion especially if located on the neck mimicking antemortem injuries. They are also occasionally misinterpreted as patterned abrasion due to the imprinted effect of a blunt or offending object. On closer inspection, artifacts made by ants can be immediately apparent especially when the ants are identified upon the body, but final diagnosis can be only confirmed at the autopsy by gross and microscopic analysis. The features of such lesions will be illustrated in detail by reviewing some interesting forensic cases.