The oviposition. and prey consumption rates of Amblyseius barkeri depend on the number of prey available. The number of eggs laid by the predator female, and the consumption of Tetranychus urticae Koch as prey, increased with increasing prey density to maximum of 1.96 eggs deposited and 20.96 devoured protonymphs per day at a prey density of 40 protonymphs. The total number of reproductive days also increased, but then declined at the highest level of prey density. As the level of prey density was increased, there was a shift in sex ratio towards an increased proportion of females.