Impact of Comingled Heterospecific Assemblages on Developmentally Based Estimates of the Post-Mortem Interval-A Study with (Meigen), (Meigen) and Robineau-Desvoidy (Diptera: Calliphoridae).

Estimates of the minimum post-mortem interval (mPMI) using the development rate of blow flies (Diptera: Calliphoridae) are common in modern forensic entomology casework. These estimates are based on single species developing in the absence of heterospecific interactions. Yet, in real-world situations, it is not uncommon to have 2 or more blow fly species developing on a body. Species interactions have the potential to change the acceptance of resources as suitable for oviposition, the timing of oviposition, growth rate, size and development time of immature stages, as well as impacting the survival of immature stages to reach adult. This study measured larval development and growth rate of the blow flies (Meigen, 1826), (Meigen, 1826) and Robineau-Desvoidy (Diptera: Calliphoridae) over five constant temperatures (15, 20, 25, 30, 35 °C), in the presence of conspecifics or two-species heterospecific assemblages. Temperature and species treatment interacted such that larvae gained mass more rapidly when in the presence of at 20 and 30 °C, however only developed faster at first instar. At later stages, the presence of slowed development of immatures. Development time of immatures was not affected by the presence of , however larvae gained mass more slowly. Development time of immatures was faster in the presence of either or until third instar, at which point, the presence of was neutral whereas negatively impacted development time. larvae gained mass more rapidly in the presence of at 20 °C but were negatively impacted at 25 °C by the presence of either or . The results of this study indicate that metrics such as development time or larval mass used for estimating mPMI with blow flies are impacted by the presence of comingled heterospecific blow fly assemblages. As the effects of heterospecific assemblages are not uniformly positive or negative between stages, temperatures or species combinations, more research into these effects is vital. Until then, caution should be used when estimating mPMI in cases with multiple blow fly species interacting on a body.