Abstract
The indigenous phytoseiid mites, Neoseiulus cucumeris (Oudemans), N. barkeri (Hughes) and Typhlodrompis swirskii (Athias-Henriot) were collected from plants growing in different sites in Qassim region in 2013. The present study aimed to determine the effect of different rates of crowding on their feeding capacity and fecundity when they fed on the two-spotted spider mite, Tetranychus urticae Koch under laboratory conditions of 26 +/- 1 degrees C and 70 +/- 5% RH. Densities of 1, 2, 3, 4 and 5 predatory mite females per arena were provided with surplus of the prey for 10 successive days. Feeding capacity of N. barkeri and N. cucumeris, represented by number of consumed preys, increased linearly by increasing their density until reached highest rates of prey consumption when the three predators were kept together in each arena. More than three predatory mites/arena decreased directly feeding capacity. However, T. swirskii reached its highest rate of prey consumption when four mites were kept together in each arena, while its feeding capacity decreased as the density increased. Female fecundity generally decreased by increasing predator density/arena. However, T. swirskii was the most predatory species that was affected by crowding (b = - 0.27), followed by N cucumeris (b = - 0.17), while N. barkeri came last (b = - 0.07).