Estimating the time of insect colonization of catfish carrion – validating data for use in wildlife forensic investigations

A fundamental application of forensic entomology is using insects to estimate the time of colonization (TOC) of a carcass, which is associated with its post-mortem interval. Studies on how different animal tissues impact the growth patterns of forensically relevant insect larvae are common in forensic entomology, but they largely aim to provide the most accurate measurements for human cases. The Forensic Laboratory for Investigative Entomological Sciences (FLIES) Facility has provided TOC estimates for a variety of veterinary and wildlife investigations, but there are limitations with applying data from insects grown on taxa different to that of the deceased. Previous research has demonstrated that tissue type impacts fly development, which in turn impacts accuracy when estimating TOC. Furthermore, little to no data exist on the application of published data sets to cases of wildlife importance. To translate these findings for use in veterinary and wildlife forensic investigations, channel catfish (Ictalurus punctatus) were euthanized and immediately placed in the field, then monitored for fly colonization. Two daily samples were taken - one preserved and one reared to adulthood - then identified. Using previously published data sets on the development of these species, age was estimated to determine accuracy and precision as related to the time of placement and time of death of the fish specimen.