Validating the use of a local developmental data set for Chrysomya rufifacies (Diptera: Calliphoridae) to estimate the time of placement of various carrion types and sizes in Texas, USA during summer

Validating blow fly developmental datasets for estimating the time of colonization (TOC) of vertebrate remains is a critical component of applied forensic entomology. Reliable developmental data enhance the probative value of entomological evidence in forensic investigations; however, direct assessment of TOC under field conditions is inherently challenging because the timing of oviposition is rarely known. To address this limitation, previous studies have used time of placement (TOP) as a proxy for TOC to evaluate insect colonization patterns on carcasses deployed in the field. The present study evaluated the accuracy, precision, and error structure of TOP ratio estimates across multiple whole-carrion resources, focusing on the effects of thermal summation method, developmental study tissue type, species coexistence, and adult eclosion timing. Field experiments were conducted during summer months in Texas, USA, using the invasive and predatory blow fly Chrysomya rufifacies (Macquart). Results demonstrated that TOP ratios generated using accumulated degree days (ADD) were approximately 5% better aligned with known placement intervals than those derived from accumulated degree hours (ADH). Estimates based on first-emerging adults were 18% better aligned than those based on last-emerging adults, and developmental datasets generated from equine or porcine tissue produced TOP ratios that were 10% better aligned than those from canine tissue. Estimates derived from single-species development of Ch. rufifacies were substantially more precise, exhibiting up to 80% less variability than estimates from mixed-species contexts involving its intraguild prey, Cochliomyia macellaria (Fabricius). However, this increased precision was accompanied by reduced accuracy, with misalignment increasing by as much as 57% depending on carrion type. Collectively, these findings emphasize the importance of both developmental dataset selection and ecological realism when applying thermal-based models in forensic entomology.