Biology of the two spotted spider mite, Tetranychus urticae Koch was studied at constant temperatures of 26º and 30ºC. A temperature of 30º was found to be the most favorable temperatures for the development and multiplication of this pest. Threshold temperatures (t₀) of 12.87º, 12.92º, 9.45º, and 13.94 ºC were calculated for the egg, larvae, protonymph and deutonymphal stages, respectively. Based on these thresholds the stages respectively needed about 63.35, 26.81, 30.95, and 26.17 day-degrees to complete their development. Thermal units required to develop one generation of this pest was about 146.48 day-degrees using 12.50ºC as a base temperature.