The biological aspects and predation efficacy of Coccinella undecimpunctata L. fed on two aphid species namely; Rhopalosiphum padi (L.) and Schizaphis graminum (Rond.), colonized on wheat plants were studied under laboratory conditions of 26±1ºC and 65±5% RH. The obtained data are summarized as follow: The 1st , 2nd , 3rd and 4th larval durations averaged 2.50, 3.00, 3.17 and 4.00 days when the larvae of the predator were fed on R. padi , respectively , wheras it was 2.00, 3.75, 3.58 and 4.25 days on S. graminum , successively. The total larval duration lasted an average of 12.67 and 13.58 days on R. padi (L.) and S. graminum , respectively. The total developmental period was 23.58 and 25.58 days on R. padi and S. graminum, successively. The total consumption aphids during the larval stage varied according to aphid species as it averaged 340.67 and 321.33 aphids on R. padi and S. graminum, respectively. The 4th larval instar is the most efficient as they consumed 57.20 and 54.40 % of the total consumed preys, when the larvae of predator were fed on R. padi and S. graminum, successively. The pupal stage lasted an average of 5.17 and 6.0 days of the previously prey species, consecutively. The shortest and longest oviposition period of C. undecimpunctata was 66.29 and 72.86 days on R. padi and S. graminum, respectively. The total consumed preys during the pre-oviposition, oviposition, post- oviposition periods averaged 104.08, 332.75 and 226.50 aphids per female on R. padi, wheras it was 119.75, 398.67 and 269.50 preys on S. graminum, respectively. The highest mean number of eggs laid per female was 521.42 eggs was noticed on S. graminum. While the lowest value of 480.25 eggs was recorded on R. padi. Rearing on S. graminum gave the best results for egg hatching (89.33%). Longevity of female was prolonged (82.14 days) on S. graminum and was shortened (31.29 days) on R. padi. The total consumed aphids by the adult averaged 584.17and 729.17 preys per female on R. padi and S. graminum, successively. The adult female is considered the most efficient predatory stage as it consumed about 1.8 and 2.3 times as much as that of the larva on R. padi (L.) and S. graminum, consecutively.