Larval cannibalism and population dynamics of dragonflies

Cannibalism, the process of killing and eating conspecifics, is common among odonate larvae and is believed to influence odonate population dynamics. Here we attempt to summarize and consider interactions among key factors linked to cannibalism at both the individual and population levels. Through cannibalism, odonate larvae receive energy directly from the consumption of the conspecific, and indirectly from reduced exploitation competition because the per capita food supply may increase. Cannibalism might, however, also incur costs such as risk of death and pathogen infections. Alternative food availability, population density and size structure of the cannibalistic population, and habitat structure are environmental factors that affect cannibalism rate in odonate larvae on a short-term basis. Theoretical models predict that cannibalism reduces size variation under most cannibalism intensities and life histories. The models also show that cannibalism can - but will not always - stabilize population dynamics. Unfortunately few long-term studies examining the population dynamics on dragonfly larvae have been performed, and we urge more such studies.