Coleomegilla maculata (DeGeer) and Hippodamia convergens Guérin-Méneville larvae were supplied daily with ≈1.2, 2.2, 4.3, 8.2, or 16.4 mg of Acyrthosiphon pisum Harris reared on either alfalfa Medicago sativa L. (‘OK08’) or faba beans Vicia faba L. (‘Windsor’). Myristic acid and total fatty acid content (μg/mg aphid fresh weight) were 6.3 and 2.7 times greater, respectively, in pea aphids reared on alfalfa as compared with faba beans, resulting in a 1.17-fold increase in caloric content. Higher survival ratios were observed for both C. maculata and H. convergens supplied with low daily prey levels of pea aphids reared on alfalfa versus faba beans, but no differences were observed at higher prey levels. When pea aphids reared on alfalfa were supplied to C. maculata and H. convergens larvae at low prey levels, preimaginal developmental times were significantly reduced compared with those supplied with pea aphids reared on faba beans at the same prey levels. At higher daily pea aphid levels, C. maculata and H. convergens developmental times were not significantly different between host plants. At lower daily prey levels, C. maculata and H. convergens elliptical body area was larger when supplied with pea aphids reared on alfalfa, but body areas were similar at higher daily prey levels. Convergence of survival ratios, developmental times, and elliptical body areas for C. maculata and H. convergens at high (less limiting) prey levels supports the hypothesis that differences in prey nutritional value between pea aphids reared on alfalfa versus faba beans are quantitative and appear to be primarily influenced by differences in pea aphid myristic acid content.