The biological aspects of two aphid species, Aphis gossypii, and Aphis craccivora reared on three citrus varieties (Citrus sinensis, C. reticulate, C. aurantifolia) were studied under green house conditions of the Faculty of Agriculture, Menoufia University. The obtained results showed that the biological aspects were varied among the three citrus varieties. The longest generation  period for both aphid species under study were 14.21 days as overall average for Aphis gossypii and 16.86 days for Aphis craccivora on lime seedlings , whereas the shortest generation period was recorded on Navel orange as 10.25 and 10.58 days for A. gossypii, A. craccivora , respectively. The longest parturition  period for A. gossypii were 13.58 days as overall average on mandarin and was 10.72 days for A. craccivora on navel orange , whereas the shortest parturition period was recorded on lime as 9.88  for A. gossypii, and 9.18 days for A. craccivora on lime seedlings. The longest averages of life cycle was recorded for A. gossypii on mandarin as 26.11 days , and it  was 27.0 days for A. craccivora on lime , whereas the shortest life cycle was recorded on navel orange as 23.66 days  for A. gossypii, and 9.18 days for A. craccivora on the same variety. As for the adult longevity , the longest  period was 17.45 days for A. gossypii females on navel orange, and was  15.05 days as overall average for A. craccivora on mandarin , whereas the shortest adult longevity  period was recorded on lime as 14.5 and 13.7 days   for A. gossypii, and A. craccivora on lime seedlings. It could be concluded that navel orange was more preferable host for the two aphid species compared with the other citrus varieties.