A comparative study of the entomofauna (Coleoptera, Diptera) associated with hanging and ground pig carcasses in a forest habitat of Poland

Suicide by hanging is one of the most common causes of death, worldwide. Therefore, studies of insects associated with hanging cadavers are important for developing entomological tools capable of estimating the postmortem intervals in such cases. We conducted a two-year experiment, in the spring, summer, and autumn of 2012 and 2013, studying the entomofauna of 12 hanging and 12 ground, decomposing pig carcasses in a hornbeam-oak forest, in western Poland. Both carcass treatments showed colonization by similar insect species. Among the 224 taxa collected, 61 and 52 were minimally abundant (>/=10 individuals) during the adult stage on at least one hanging and at least one ground carcass, respectively. During the spring and autumn, more adult flies were attracted to hanging carcasses, whereas during the summer, their numbers were similar on both hanging and ground carcasses. Adult beetles were higher in number on hanging carcasses during the spring, but during the summer and autumn, they were slightly more abundant on ground pig carcasses. Irrespective of the carcass treatment, Dryomyzidae, Muscidae, and Piophilidae were the most abundant flies, whereas representatives of Geotrupidae, Histeridae, and Silphidae were the dominant families in the studied beetle community. Only Anoplotrupes stercorosus (Scriba) and Hydrotaea similis Meade adults and Calliphora vomitoria (Linnaeus) larvae reached minimal abundance on all carcasses during all seasons. Carcass treatment only affected the numbers of minimally abundant fly species at the larval stage due to their higher numbers on ground pig carcasses. Although differences in the residency patterns of insects were observed between carcass treatments, they were not significant. In general, adult insects tended to be present for slightly longer times on hanging carcasses than on ground carcasses, whereas beetle larvae had longer presences on ground pig carcasses. Fly larvae were present on ground carcasses for the same amount of time as on hanging carcasses. More broken residency patterns were observed among the adult insects and beetle larvae that colonized hanging carcasses. Fly larvae that colonized ground carcasses had more breaks within the presence periods than fly larvae colonizing hanging carcasses. Neither treatment significantly affected the time of insect appearance on carrion. Most species appeared at the same time or at within one- or two-day intervals on both treatments. Seasonal differences in insect appearance were found, with most species colonizing quickly during the summer. The implications of these findings for forensic entomology are discussed.