Biological aspects of the predatory mite Neoseiulus cucumeris (Oud.) was investigated in the Laboratory at 20 , 25 and 30 Cْ  and 65 ±5% R. H To evaluate the efficieny of the predatory mite, when fed on movable stages of european red mite, Panonychus ulmi (Koch) in Egypt. The incubation period lasted (4.31&4.0), (3.6&3.2) and (2.6&2.3) days for female and male at 20,25 and 30 C., respectively. Total immature stages for female  averaged 8.85 ± 0.29 ; 5.7± 0.42 and  ; 4.6 ± 0.51 days while for male averaged  8.15 ± 0.49 ; 5.25 ± 0.34 and 4.1 ± 0.64 days at 20, 25 and 30 Cْ respectively . Female longevity was longer than  male,   this period averaged (26.65 & 18.2), (20.15 & 14.7 ) and (18.8 & 13.1 ) days at 20 , 25 and 30 respectively . Trials on predation showed that , female fed on greater number of prey individuals than male . During life span , female consumed 59.23 ± 2.03 , 92.27 ± 2.14 and 74.73 ± 1.58 prey of P. ulmi , respectively at the previous temperature while male consumed 39.78 ±1.82, 65.23 ±2.50 and 47.69±1.94 prey respectively at 20 25 and 30 Cْ