Laboratory studies with the phytoseiid mites, Metaseiulus validus and Typhloseiopsis pini, were made to assess their potential as natural control agents. The M. validus mite developed from egg to adult in about six days at 35 C, and T. pini required about eight days at 29 C. With decreasing temperature, the developmental period increased. Metaseiulus validus had a maximum fecundity rate of. 1.08 eggs/ ? per day at 29 C, and T. pini had a maximum of 0.95 at 24 C. Both species could feed, develop, and oviposit on three tetranychid species, but not on scale crawlers or tenuipalpids. Only T. pini could feed, develop, and oviposit on pollen. Metaseiulus validus consumed 2.77 eggs/ ? per day of Oligonychus punicae, and 0.81 adult ? ?; T. pini consumed 1.89 and 1.11, respectively. At an 8-h photoperiod, 88.3 percent of the ? ? of M. validus and 71.43 percent of the ? ?. of T. pini entered reproductive diapause. At a 16-h photoperiod, neither species entered diapause. The ratio of ? ? to ? ? of both species was about 1: 1. At 24 C, the preovipositional period for T. pini was 4.33 days, the reproductive longevity was 18.75 days, and 17.70 eggs were laid per ?.