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Laboratory, greenhouse, and field studies were conducted to evaluate the influence of aphid prey diet and aphid host plant on the development of the seven-spotted ladybeetle (Coccinella septempunctata L.). We evaluated the two aphid species, Myzus persicae Sulzer and Macrosiphum euphorbiae Thomas, as prey reared on potato plants, and M. persicae reared on both potato and barley plants. Development rates and weight gain of immature C. septempunctata were measured to assess the effect of diet. Prey preference of fourth instar and adult C. septempunctata for M. persicae and M. euphorbiae in a 50:50 ratio was also evaluated. M. persicae was a more suitable prey than M. euphorbiae, as indicated by greater weight gain and shorter development time in the former. Newly merged C. septempunctata adults from larvae fed M. persicae reared on potato were significantly heavier than adults from larvae fed M. persicae reared on barley. However, no difference was found in the developmental time of C. septempunctata larvae when fed M. persicae from either host plant. C. septempunctata immatures showed no preference between aphid species, but C. septempunctata adults preferred M. euphorbiae at nearly 2:1 compared to M. persicae. Searching efficiency of C. septempunctata larvae did not differ between the two crop species. However, C. septempunctata larvae are more likely to survive when foraging in barley compared to potato.