Under laboratory conditions, some biological aspects of the parasitoid O. pallipes were studied. Results obtained revealed that ovipositrion, postoviposition periods and adult longevity were significantly higher when O. pallipes female reared on the 3^rd Liriomyza trifolii (Burgess) larval instar recording (3.0±1.1, 3.1±1.1 and 6.8±1.8 days, respectively), while the immature stage was significantly shorter (27.1±3.3 days) if compared with the 2^nd instar larvae. Moreover, number of eggs/female, number of parasitized larvae were higher on the 3^rd L. trifolii larvalinstar than on the 2^nd instar larvae with insignificant differences.        Number of produced eggs in the females ovaries was significantly higher when the parasitoid females were fed on the host exudates (43.7±11.6 eggs/female) in comparison with those fed on honey or sugar solution 10% (35.6±12.3 and 28.2±5.4 eggs/female, respectively.It is interesting to mention that the starved females absorbed ≈ 40% of the eggs in their ovaries in comparison with the newly emerged ones.        Number of eggs and number of parasitized larvae per female were significantly higher (13.9±3.7 eggs/female and 9.2±2.3 host larvae/female) when 30 L. trifolii larvae were presented to O. pallipes females in comparison with 5, 10 and 20 host larvae, while number of super-parasitized larvae was significantly higher (2.6±1.1) when 5 host larvae were presented.         Number of eggs and parasitized larvae per parasitoid female were higher on L. trifolii than on L. bryonia (Blanchard) with significant differences in the choice test recording (9.2±3.9 eggs/female and 7.0±2.9 host larvae/female, respectively), while only number of parasitized larvae per female was significantly higher and also number of eggs per female was higher on L. trifolii than on L.bryonia in no–choice test with insignificant differences.