Although laboratory observations provide basic knowledge of the development and reproduction of predacious and phytophagous mites, little is known of their behavior under natural conditions. Using a closed system designed to simulate natural climate patterns, we investigated the development and reproduction of the predatory mite Neoseiulus californicus (McGregor) (Acari: Phytoseiidae) and the pest mite Tetranychus urticae Koch (Acari: Tetranychidae) at air temperatures typical of June to October at three latitudes (Aomori,Tottori, and Naha) in Japan. The peaks of development in both species showed similar trends at each location. The shortest developmental times for both species were observed during August in Aomori, from July to September in Tottori and during August and September in Naha. Development of T. urticae was not completed during October in Aomori due to the decreased air temperature. High reproduction (number of eggs produced during 5 d from the first oviposition) of N. californicus was attained at the conditions that shortened the developmental times (i.e., high-temperature months). T. urticae showed a reproduction trend similar to that of N. californicus except for the low number of eggs produced during August in Naha due to the high mortality of adult females and during October in Tottori due to diapause incidence. This information is in agreement with field observations and together might be useful for planning biological control programs for phytophagous mites and for successful establishment of predacious mites in new habitats.