Odour-mediated preference and prey preference of Macrolophus caliginosus between spider mites and green peach aphids

A comparative study between direct prey preference and odour-mediated preference of the predatory mirid bug, Macrolophus caliginosus, was conducted. We used a Y-tube olfactometer to determine the attraction of the predator to herbivore-induced volatiles from Myzus persicae or Tetranychus urticae-infested sweet pepper plants over clean plants and to direct prey odours over clean air. The mirid bugs showed a stronger response to odours from infested plants than to odours from clean plants. The mirids did, however, not seem to exploit odours emitted directly from the prey themselves. Our results further demonstrated that M. caliginosus prefers M. persicae to T. urticae in a direct two-choice consumption test. This preference was, however, not reflected in a similar odour-mediated preference between plant volatiles induced by either of the two preys. Two hypotheses are suggested for this neutral response of the mirids to herbivore-induced volatiles from a preference prey or a non-preference prey.