DO PHYTOSEIID MITES SELECT THE BEST PREY SPECIES IN TERMS OF REPRODUCTIVE SUCCESS

Optimal foraging theory predicts that predators prefer those prey species that are most rewarding in terms of reproductive success, which is dependent on prey quality and prey availability. To investigate which selection pressures may have moulded prey preference in an acarine system consisting of two prey species and three predator species, we tested whether prey preference of the predators is matched by the associated reproductive success. The predators involved are Amblyseius finlandicus (Oudemans), Am. potentillae (Garman) and Typhlodromus pyri Scheuten. The prey species are the apple rust mite (Aculus schlechtendali (Nalepa)) and the fruit-tree red spider mite (Panonychus ulmi (Koch)). Reproductive success was assessed in terms of intrinsic rate of increase and for one predator also in terms of diapause induction. All three predator species reached highest reproductive success on the same prey species: apple rust mite. This was most pronounced for the predator Am. finlandicus, because its larval stage suffered severe mortality when feeding on P. ulmi. An independent study on prey preference of the three predator species (Dicke et al., 1988) revealed that Am. finlandicus prefers Ac. schlechtendali to P. ulmi, whereas the other two predator species have the reverse preference. Thus, on the basis of current data, prey preference of Am. finlandicus can be understood in terms of reproductive success. However, this is not so for prey preference of T. pyri and Am. potentillae. Investigations needed for a better understanding of prey preference of the last-named two predator species are discussed. © 1990 Elsevier Science Publishers B.V.