The coccinellid predator Coccinella undecimpunctata is considered one of the most efficient and potential predators of many soft bodied insect pests especially aphids. The biology and predatory potential of this coccinellid were studied on the 4^th nymphal instar of two aphid species, Aphis craccivora Koch. and Schizaphis graminum (Rondani). By rearing on A. craccivora at 20, 25 and 30°C the incubation periods of C. undecimpunctata eggs were 5.84, 4.32 and 3.62 days, led subsequently, to 80.20%, 94.40% and 64.40% hatching, respectively, opposed to 5.98, 4.60 and 3.42 days with 74.40, 90.40 and 62.00% hatchability when rearing took place on S. graminum. The total larval duration lasted 9.96 days on A. craccivora, being, significantly, shorter than the 10.67 days resulted from rearing on S. graminum. Throughout the whole period of the larval stage feeding on the 4^th instar nymphs of A. craccivora and S. graminum, a single larva fed on163.54 or 170.21 nymphs, respectively. C. undecimpunctata female's longevity elapsed 64.04 and 63.19 days, respectively. A single mated female deposited 686.69 eggs when reared on A. craccivora, opposed to 590.57 eggs by feeding on S. graminum. These results concluded that rearing of C. undecimpunctata on A. craccivora proved the best to obtain immature stages of shorter durations, much lower consumption and the highest reproductivety of eggs.