Two-spotted spider mites (Tetranychus urticae) were obtained from the Laboratory of Ecological Information, Graduate School of Agriculture, Kyoto University, in 2002, and reared on kidney bean plants (Phaseolus vulgaris cv. Nagauzuramame) at 25uC with a 16 : 8 h photoperiod. Predatory mites (Phytoseiulus persimilis) were purchased from Arysta Lifescience Corporation (Tokyo, Japan) in 2009. They were reared on T. urticae living on kidney bean plants under the same climate conditions as the spider mites.