Diet of a polyphagous arthropod predator affects refuge seeking of its thrips prey

Antipredator behaviour of prey costs time and energy, at the expense of oth er activities. However, not all predators are equally dangerous to all prey some may have switched to feeding on another prey species, making them eff ectively harmless. To minimize costs, prey should therefore invest in antip redator behaviour only when dangerous predators are around. To distinguish these from harmless predators, prey may use cues related to predation on co nspecifics, such as odours released by a predator that has recently eaten c onspecific prey or alarm pheromones released by attacked prey. We studied r efuge use by a herbivorous/omnivorous thrips, Frankliniella occinentalis, i n response to odours associated with a generalist predatory bug, Orius laev igatus, fed either with conspecific thrips or with other prey. The refuge u sed by thrips larvae is the web produced by its competitor, the two-spotted spider mite, Tetranychus urticae, where thrips larvae experience lower pre dation risk because the predatory bug is hindered by the web. Thrips larvae moved into this refuge when odours associated with predatory bugs that had previously fed on thrips were present, whereas odours from predatory bugs that had fed on other prey had less effect. We discuss the consequences of this antipredator behaviour for population dynamics. (C) 2000 The Associati on for the Study of Animal Behaviour.