Abstract: Predatory mites contained in an enclosed housing are provided with a continuous food source (i.e. spidermites) so that the healthy adult predatory mites migrate upwards to a collection container at the apex of the housing where a user harvests the predatory mites. The predatory mites are provided with spidermite-infested vegetation disposed in planar trays. The trays are chronologically arranged in a vertical stack within the housing so that as new trays loaded with spidermites are added to the top of the stack, old trays depleted of spidermites are removed from the bottom of the stack. The predatory mites intuitively display negative geotropism and positive phototropism so that the mites naturally move upwards and toward the light. Consequently the predatory mites migrate to the upper trays as new trays are added and eventually reach the collection container at the apex of the housing.