Abstract: Results of the experiments conducted at the temperatures of 19, 22, 25, 28 and 31°C in the laboratory showed that the threshold temperatures of the egg, nymph and female imago of Amblyseius nicholsi were 21.1,10.74, 8.4 and 7.4°C, respectively, and the effective accumulative temperatures were 25.4,12.2,34.4 and 530.9 day-degrees, respectively. The optimal temperature for the development of the predator was between 22°C and 25°C. At a constant temperature of 25°C, the developmental rates of the egg, larva, nymph and female imago were 1.96,0.89,2.09 and 30.47 days, respectively, while hatching rate of eggs and the survival rates of larvae, the first and the second instar nymphs were over 96%. The highest average total as well as daily oviposition (42.9 and 2.4, respectively) were obtained at the constant temperature of 25°C. The innate capacity for increase (rm), the finite rate of increase (A), the mean length of a generation and the net reproductive rate (Ro) of the experimental population were 0.1819,1.1994, 3.8116, and 28.0265, respectively.