Maggot Mass Effect on the Development and Survival of Forensically Important Blow Flies

This study investigates how larval density and associated temperature changes affect the development and survival of two forensically essential blow fly species, <i>Lucilia sericata</i> and <i>Calliphora vicina</i>. Larvae colonies were reared at 25 °C under controlled conditions, with adults at 23.3 °C on a 16:8 light cycle. Using a split-plot design, we tested four larval densities of 50, 200, 1000, and 2000 individuals at 25 °C and 30 °C, with temperature gradients measured via thermocouple at four mass positions three times daily, and larvae fed liver at ca. 6 g/50 larvae. Key findings revealed density-dependent developmental patterns, with 1000 larvae representing a 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 due to hypoxia and waste accumulation. <i>L. sericata</i> demonstrated greater thermal tolerance than <i>C. vicina</i>, particularly at 30 °C, as <i>C. vicina</i> showed 58% reduced emergence. We demonstrated that maggot mass temperature might not be reliable, as they may overestimate developmental rate by 18-22% at densities over 1000 larvae. We recommend a bigger container for maggot mass-related studies, starting with 1000 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.