Abstract: Some biological data of the phytoseiid mite species Euseius metwallyi were investigated to evaluate its ability in controlling the two-spotted spider mite Tetranychus urticae Koch on certain fruit trees under laboratory condition of 28±2°C and 74±4% R.H. Adult E. metwallyi females were reared singly during their adulthood on apple, apricot, fig, grape and peach leaf discs and provided daily with constant number of T. urticae immature stages and adult females (5 preys/predator female). The predator appear more efficient on T. urticae immature stages. Adult female longevity, prey consumption and fecundity were significantly differed between leaves of the tested plants. The longest longevity (15.4 and 16.4 days), the greatest prey consumption (35.2 and 65.2 preys) and the highest fecundity (10.2 and 12.6 eggs) were recorded on peach leaves when feeding on T. urticae adult females and immature stages, respectively. On the other hand the shortest longevity (9.4 and 10.2 days), the lowest prey consumption (21.6 and 34.8 preys) and the least fecundity (3.8 and 4.2 eggs) were recorded on apricot leaves, when predator female fed on T. urticae adult females and immature stages respectively. The shortest duration period (4.4 days) and the highest prey consumption (18 preys) of E. metwallyi nymphal stages were recorded when feeding on T. urticae larvae. Predator female consumed significantly more preys (43.6 preys) and deposited significantly greater number of eggs (14.00 eggs) when feeding on T. urticae larvae than other prey stages. These results indicated that, plant leaf surface and prey stage are important factors affecting efficiency of this predator against the investigated prey pest.