The effect of postmortem penetrative trauma on oviposition behavior of Calliphora vicina

Abstract

Flies in the family Calliphoridae are purported to demonstrate a strong attraction to and preferential colonization of wounds when present on human corpses or carrion. This well-circulated concept in Forensic Entomology is based on surprisingly few empirical studies that have examined the oviposition behavior of necrophagous Diptera toward wounds of vertebrate animals. In the present study, the oviposition behavior of Calliphora vicina toward piglets inflicted with postmortem sharp force trauma was examined during a 10-h test period under controlled laboratory conditions and in an outdoor urban environment. Three species of flies (C. vicina, C. livida and Cynomya cadaverina) deposited eggs on wounded and non-wound piglets during the field studies, although more than 80% of all eggs laid were by C. vicina regardless of wound status. For all species, oviposition occurred predominately on the head, including in eyes, ears, nose and mouth, and less frequently in other locations on the body. Eggs were never found in or near wounds. Similar oviposition patterns were displayed by C. vicina under laboratory conditions, with the exception for limited egg deposition in wounds under overcrowded conditions. In this latter scenario, egg deposition represented only 0.14% of the total reproductive output of adult flies. The findings do not support the contention that calliphorids preferentially oviposit in wounds resulting from sharp force penetrating trauma.