Competition, Cannibalism, and Size Class Dominance in a Dragonfly

Abstract

This paper reports the consequences of size class interactions among larvae of the dragonfly Aeshna juncea inhabiting splash pools on the shores of Isle Royale, in Lake Superior, USA. This dragonfly has a three-year life cycle, and there was a close correspondence between age and size classes. Observations of dragonfly behavior and samples of fecal contents both suggested that larvae were aggressive toward conspecifics and that cannibalism was common. Experiments in plastic containers and natural pools demonstrated that two-year-old dragonflies were more secretive and experienced higher mortality in the presence of larger three-year-old larvae