This study was conducted to determine the effect of different temperatures and prey type on the biology of Euseius scutalis Athias-Henriot (Acari: Phytoseiidae) fed on Tetranychus urticae Koch and Panonychus ulmi (Koch) (Acari: Tetranychidae) at 20, 25 and 30°C. The incubation period of E. scutalis was shortened with increasing temperature. The mean duration of immature stages was 10.3, 12.7; 7.0, 9.8 and 4.1, 5.7 days when the mite females fed on T. urticae and P. ulmi at 20,25 and 30°C, respectively. The life cycle duration was 14.0, 15.5; 9.1, 12.4 and 5.6, 7.9 days when the females were fed on the aforementioned conditions, respectively. Average female longevity on T. urticae and P. ulmi was 27.7& 31.9 days at 20°C, followed by 22.4& 25.7 days at 25°C and 15.7& 20.4 days at 30°C, respectively. The maximum average fecundity (44.2 eggs/female) was observed at 25°C when females fed on T. urticae compared with 35.6 eggs/female on P. ulmi. Obtained relative values for males were generally less than those of females. Effect of temperature on obtained biological values expressed as rates (1/duration) between main aspects and tested temperatures was significant. Obtained R² values ranged between 0.90 and 0.655 with P < 0.001. It was concluded that T. urticae was preferred prey than P. ulmi and 30°C was the best for individual developmental rate while 25°C was the best for most fecundity regardless tested prey.