Schizotetranychus longus Saito is a common pest of bamboo in Japan. We report its new occurrence in the Willamette Valley, Oregon, on bamboo. We assessed the ability of adult females of Neoseiulus fallacis (Garman), a native predaceous mite, to invade S. longus nests after construction times of 5 or 10 days. Frequency of predators in nests decreased from 5 to 10 days, although the predator laid most of its eggs in nests irrespective of construction time. In choice tests, spider mile webbing was more attractive to A. fallacis than eggs, but similar to feces. Predators searched more in proximity to feces than eggs, but resting sites were equally common near both. Survival, activity and reproduction of N. fallacis when given ex:cess of mixed life stages of S. longus, Tetranychus urticae Koch, pollen of Tulipa gesneriana L. or Pseudotsuga menzesii (Mirbel), or no food were measured by holding single adult female N. fallacis for 7 days. Survival, activity, oviposition and immature production of predators were alike for both spider mites, but lower (or higher activity) with pollens or when starved. To see if N. fallacis would suppress S. longus under normal growing conditions, predators were added to infested Sasaella hidaensis (Makino and Uchida) var. Murai plants, and mites were monitored thereafter for 5 weeks. N. fallacis significantly reduced levels of S. longus and the rates that it infested bamboo leaves; it nearly eliminated S. longus from plants at the end of the test.