Prey selection by dragonflies in relation to prey size and wasp-like colours and patterns

Although most of the studies on the evolution of mimicry and warning signals in insects have considered birds as the main predators, predation by other taxonomic groups, such as insects, may far exceed avian predation at some localities. However, few studies have investigated the possibility that insect predators might facilitate selection for warning colours and mimicry in other insects. We experimentally evaluated whether prey size and/or wasp-like colours and patterns were important in deterring attacks by dragonflies, using pairwise and single presentations of both natural and artificial prey in the field. Dragonflies were more likely to attack smaller natural prey and smaller artificial prey. However, dragonflies showed no differences between attacks on prey with wasp-like colours and patterns and those on the same-sized prey that were nonmimetic. Moreover, dragonflies avoided attacking both mock-painted and black-painted wasps entirely. Overall, we found no evidence to support the hypothesis that wasp-like warning signals protect small insect prey from attack by dragonflies, although size seems to be an important cue in dragonfly prey choice.