Foraging behaviour of the damselfly larva Pyrrhosoma nymphula (Sulzer) in response to predator presence (Zygoptera: Coenagrionidae)

The trade off between foraging and predator avoidance was studied. In the presence of a larva of the predatory Aeshna juncea, R nymphula was found to reduce foraging activity significantly. P. nymphula reduced foraging activity in response to chemical stimuli from A. juncea but not in response to visual stimuli. Foraging activity was further reduced when the diet of A. juncea was changed from chironomid larvae to P. nymphula. This suggests that predators are detected chemically and are chemically labelled by their diet. Foraging activity was found to increase with starvation level after 48 h without access to food, with a further increase after 72 h of starvation. The presence of chemical stimuli from conspecific fed predators delayed the increase in foraging activity until 72 h of starvation. These results have implications for larval survival and adult reproductive fitness.