Environmental Drivers of Blowfly Pre-Colonization Interval on Human Remains in Forensic Entomology

Background: Accurate estimation of the pre-colonization interval (pre-CI), defined as the period between body deposition and initial insect oviposition, remains a challenge in postmortem interval estimation in forensic entomology. This study quantified the effects of environmental and contextual variables on blowfly oviposition timing using human cadavers. Methods: Daily photographic records from 203 donated cadavers placed at the University of Tennessee Anthropology Research Facility (March 2011–July 2014) were used to document the first observed oviposition of blowflies. Multivariable general linear models evaluated the effects of monthly temperature, black plastic coverage, and pre-placement soft tissue damage on calendar days to oviposition (IOday) and accumulated degree days (IOADD). Results: Temperature was the dominant predictor, explaining substantial variation in pre-CI. Black plastic coverage significantly delayed oviposition and exhibited a temperature-dependent effect. Although soft tissue damage was associated with earlier oviposition in univariable analyses, it did not remain significant in multivariable models. Cold conditions were associated with prolonged and highly variable pre-CI. Conclusions: These findings demonstrate that temperature was the strongest predictor in this observational dataset, while contextual factors such as physical barriers modify colonization patterns. Together, they highlight the need to incorporate environmental and contextual variables into PMI estimation models and support more defensible interpretations of entomological evidence, particularly in cases involving delayed colonization or restricted insect access.