Leaf damage and prey type determine search effort in Orius tristicolor

Components of search effort were determined for adult females of Orius tris ticolor (White) (Hemiptera: Anthocoridae) on bean, Phaseolus vulgaris L., l eaves with either western flower thrips, Frankliniella occidentalis (Pergan de) (Thysanoptera: Thripidae) or twospotted spider mites, Tetranychus urtic ae (Koch) (Acari: Tetranychidae) as prey. In the absence of prey, females o f O. tristicolor allocated significantly more search time to leaves damaged by western flower thrips than to leaves damaged by twospotted spider mites , artificially damaged leaves or undamaged leaves. In the presence of prey, search time increased with increasing amounts of leaf damage for both prey species, but was not affected by prey species. Amounts of leaf damage or t ype of prey did not affect giving-up-time. The proportion of predators that successfully located thrips increased with increasing amounts of thrips da mage on leaves. Females of O. tristicolor appeared to follow some simple, b ehavioural rules-of-thumb for allocation of search effort. The presence and type of damage determined the initial effort allocated to searching a leaf . Subsequent effort was determined by successful capture of prey, regardles s of species. The implications of these results for application of Orius sp p. for biological control are discussed.