Abstract
The effectiveness of the mite Phytoseiulus persimilis Athias-Henriot as a predator of the two-spotted spider mite. Tetranychus urticae (Koch) was studied in plant-growth chambers held at constant temperatures of 15, 20, 25, and 30°C. Lima bean seedlings were infested with eggs of the predator and adults of the prey. Both populations were sampled periodically, and counts were made. Excellent control of T. urticae occurred at 20°C, and somewhat poorer control at 15 and 25°C. There was no apparent control by the predator at 30°C. Some cryptic factor affected the prey population numbers at this temperature.