INFLUENCE OF THE SPATIAL-DISTRIBUTION PATTERN OF PREY AMONG PATCHES AND SPATIAL COINCIDENCE ON THE FUNCTIONAL AND NUMERICAL RESPONSE OF PHYTOSEIULUS-PERSIMILIS (ACARINA, PHYTOSEIIDAE)

In a model system composed of 16 leaf disks (Phaseolus vulgaris L.) di stributed uniformly in an arena (50 x 50 cm), the influence of both th e spatial dispersion pattern of prey (eggs of Tetranychus urticae Koch ) and the transit time of the predator between patches (leaf disks) on the overall functional and numerical response of Phytoseiulus persimi lis Athias-Henriot was studied. Regardless of the pattern of the prey and the transit time of the predator, the functional response curves s howed the response type 2. The handling time of the predator became si gnificantly longer when the prey was in contagious pattern than in uni form pattern (1.52-1.60 versus 0.68-0.90 h). The number of prey consum ed and the number of eggs laid per female P. persimilis decreased sign ificantly at the initial prey density, which was more than 20 per patc h. When the transit time of the predator was long, the effects of coin cidence between predator and prey on both the number of prey and the n umber of eggs of the predator were significant. Low degree of spatial coincidence merely reduced the number of prey consumed and the number of eggs laid per predator. The number of eggs per predator was not rel ated to the prey density at this condition. Based on these results, it was suggested that a density-dependent dispersion pattern of prey and coincidence can determine the overall functional response type of the predator in a complex system consisting of many heterogenous patches, such as in fields, and that the prey density-dependent functional res ponse of the predator could be possible.