The biology of the cotton aphid, Aphis gossypii on Cucumber plants, Cucumis sativus, and the green peach aphid, Myzus persicae on hot pepper plants, Capsicum annuum carried out at late 2018 Winter and early 2018 Summer, under semi-field conditions at a greenhouse in El Kom El Akhdar, Shebin El Kom, Menoufia, Egypt. Also, the accumulative population produced from one viviparous of A. gossypii & M. persicae female reared at the summer season under controlled conditions was determined. The results showed that the average life cycle of A. gossypii in winter was 8.4 days and the life span was 20.8 days, while in summer, the life cycle was 6.8 days, with 13.2 days as life span. The green peach aphid, M. persicae show some differences, the average life cycle of M. persicae in winter was 7.2 days, with 36 days as life span, 4.2 days, and 21 days in summer. The epidemiology of the two aphid species studied by isolating one viviparous female on a non-infested plant and estimating the number of insects on the plant after one and two weeks. The average number of A. gossypii population was 25 individuals after one week, which was higher than that of the green peach, M. persicae recording 16.3 individuals. After two weeks, M. persicae occupied the first rank producing 518 individuals, compared with 462.3 individuals for that of A. gossypii.