Predator-prey responses in an acarine system

Summary This study examines the responses of the predatory mite,Phytoseiulus persimilis, to the density and distribution of its prey,Tetranychus urticae. It is divided into three parts. Firstly, the functional responses of protonymph, deutonymph and adult females towards different prey stages are displayed. The great majority of the responses are of the type II form, and the variations in the values of attack ratea′ and handling timeT _h are discussed. Experiments are then described in which individual protonymph, deutonymph and adult female predators are presented with varying ratios of two prey age-classes (eggs and deutonymphs, and larvae and deutonymphs). Any observed preference for one of the prey stages is discussed in relation to the predicted preference on the basis of the separate functional response experiments. Finally, the response of different densities of adult female predators to a non-random distribution of deutonymph prey on bean leaflets is examined. The predators show a clear tendency to aggregate on the leaflets of high prey density, counteracted to some extent by interference increasing the probability of dispersal to other leaflets.