Estimating Post-mortem Intervals of Wildlife Carcasses Using Necrophilous Insects

The succession and species composition of necrophilous insects on animal carcasses can be used by wildlife law enforcement officers for estimating postmortem interval (PMI) at suspicious death scenes. Necrophilous insects infesting wildlife carcasses (Louisiana black bear, white-tailed deer, and alligator) in a woodland habitat were monitored during the spring of 1999 to eventually develop a guide for estimating PMI by wildlife officers based on an insect database. The study was conducted at the Waddill Outdoor Educational Center in East Baton Rouge Parish, Louisiana. An overview of the study is provided herein based on sampling of aerial and ground inhabitating necrophilous insects associated with the carcasses. Sixty-five species of insects were manually collected during the spring study (20 fly species, 33 beetle species, and an assortment of spiders, mites, and other miscellaneous insects of minor forensic importance). On Day 1, adult green blow flies (Phaenicia coeruleiviridis [MacQuart]) and black blow flies (Phormia regina [Meigen]) were the initial insects associated with the carcasses. Blow fly egg masses were commonly found by Day 2 and were generally located in the mouths and head regions of all carcasses. Soldier flies (Hermetia illucens [L.]) became associated with the bear carcass by Day 11 and continued until Day 92 (end of the test). Due to the decomposition of the other carcasses, soldier fly immatures were not found at any other carcass site. Beetles were the second wave of insects associated the carcasses and consisted of both predatory and scavenger species. Skin beetles, which prefer the more advanced decaying carcass stage, were not found on alligators but were collected from all other carcasses. At least some representatives of predator ants species (red imported fire ant, acrobat ant, and carpenter ant) were found from Day 2 until complete decomposition of the wildlife carcasses.

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