Maggot Mass Effect on the Development and Survival of Forensic Blow Flies

Forensic entomology scientists use blow flies' developing patterns to estimate the postmortem interval (PMI). However, larval aggregations produce metabolic heat, resulting in complex microclimates that may change growth timetables. This study investigates how larval density and associated temperature changes affect the development and survival of two forensically essential blow fly species, Lucilia sericata and Calliphora vicina. This study examined how larval density and associated thermal profiles affect the development of both blow fly species. Using a split-plot design, we tested four larval densities at 25°C and 30°C, with temperature gradients measured via thermocouple at four mass positions three times daily. We recorded the number of pupae and measured the larvae’s weight to assess the extent of the density effect on the blow flies studied. Key findings revealed density-dependent developmental patterns, with 1,000 larvae representing an optimal threshold where thermoregulatory benefits balance competition costs. Temperature gradients showed edge-to-center differentials up to 5.2°C, yet high-density masses exhibited prolonged development despite warmer microclimates. L. sericata demonstrated greater thermal tolerance than C. vicina, particularly at 30°C. Lethal temperature assays revealed species-specific survival thresholds, with preconditioning enhancing heat resistance in L. sericata but not C. vomitoria. These results demonstrated that maggot mass temperature might not be reliable, as it may overestimate the developmental rate. We recommend a bigger container for maggot mass-related studies, starting with 1,000 larvae per container. The study provides a framework for density-adjusted ADD models and highlights climate change implications for blow fly communication dynamics in forensics contexts. Advisor: Leon Higley