The spider mite, Tetranychus urticae (Acari: Tetranychidae) is the main pest of various crops and trees. This study was conducted to evaluate the efficacy of the predacious mite, Neoseiulus bellinus (womersleyi) (Acari: Phytoseiidae), in checking Tetranychus urticae at different temperatures and 70% relative humidity.The  developmental periods of different immature stages decreased with increasing temperature and the life cycle for female was 9.12±1.2 and male were 7.8 ± 0.67 days  at 30°C. However the development time was 14.18 ± 1.77 for female and 12.2±1.32 for male at 20°C.The pre- and post-oviposition period and female longevity all shortened as temperature increased. The longest oviposition period was observed at 20°C as 26.62 ± 3.3 days.While at 30 ° C 24.5±2.9 days.  The mated females laid an average 5.99 ± 1.39 and 11.69 ± 0.7 eggs per day, respectively. The life cycle for all immature stages tended to decrease as the light period increased indicating that immature development as well as diapause induction are affected by photoperiod and further suggest that diapause-inducing stimuli prolong the developmental period especially for the deutonymphal stage.