Thermal requirements of Amblyseius sp. fed with Tetranychus urticae at five constant temperatures (17, 20, 24, 27 y 31°C) were studied. The stages of egg, larva, protonymph, deutonymph and adult egg corresponded to temperature thresholds of 12,6; 13,1; 11,6; 13,4 and 12,7 °C, and thermal constants of 26,6; 10,2; 16,1; 13,3 and 66,1 °D, respectively.