Functional and Numerical Responses of the Predatory Mite, Amblyseius fallacis,1 to Prey Density

Abstract

Feeding rate and egg deposition rate of the predatory mite Amblyseius fallacis (Garman) was studied in response to the density of 3 different stages of the prey Tetranyehus urticae (Koch). Predation rate and egg deposition rate depended on the density of the prey up to a maximum. The form of the curve depended on the type of prey. When the prey was in the egg stage, there was a linear relationship between number of prey attacked/predator and prey density, up to a density of 40 per leaf. When the prey was adult ♂, there was a linear response by predators to prey density up to a maximum of 40 prey per leaf. However, in contrast to egg-stage prey, as the density of the ♂ prey was further increased so was the attack rate of the predator. As the density of the ♀ prey was increased the predator attacked the eggs deposited by the ♀ rather than the bigger, active ♀. The number of eggs deposited by the predator depended on the density of the prey, up to a maximum of about 2 eggs/♀/day and then the oviposition rate leveled off. The maximum rate of oviposition was reached before maximum prey attacked.