Balance between larval and pupal development time in carrion blowflies

Several studies have highlighted the impact of environmental factors such as food type or larval density on the development of blowfly larvae. We investigated how changes in development speed (due to larval density and group composition) are divided among feeding and post-feeding stages. Even if these parameters impinge only on feeding larvae, they may ultimately also affect their subsequent development, and especially metamorphosis duration. Therefore, this study analysed the effect of larval density and group composition on the rhythm of necrophagous blowfly development. Based on laboratory studies, we highlighted that Calliphora vicina individuals with a fast development during their feeding phase developed slower in the later post-feeding phase (i.e., they had a compensatory effect). Lucilia sericata, a calliphorid species also frequently found on carrion at the same time as C. vicina, showed a different developmental strategy by not making its post-larval development speed dependent on the larval development speed. Finally, while a compensatory effect may exist, variations in the development rate more often accumulate through life-stages and resulted in a larger variability for later development instars. In this respect, the inclusion of detailed development duration covering all life stages, including post-feeding, is recommended in future studies, especially those dedicated to forensic entomology.