The suitability of Myzus lythri (Schrank) (Homoptera: Aphididae) and Galerucella calmariensis L. (Coleoptera: Chrysomelidae), herbivores of purple loosestrife, for preimaginal development and survival of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), Coleomegilla maculata (DeGeer) (Coleoptera: Coccinellidae), and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) was quantified to provide a more complete understanding of predator–prey relationships in the purple loosestrife (Lythrum salicaria L.) system. Individual first- or second-instar predators were assigned to one of four diets: (1) a control diet, Acyrthosiphon pisum (Harris) (Homoptera: Aphididae) or a combination of A. pisum and Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs; (2) M. lythri nymphs and adults; (3) G. calmariensis eggs; or (4) G. calmariensis larvae. Preimaginal survival of C. carnea was similar for all diets and ranged from 61 to 76% on G. calmariensis larvae, M. lythri, and the control diet. Preimaginal survival of H. axyridis ranged from 27% on G. calmariensis larvae to >80% on M. lythri and the control diet. Preimaginal survival of C. maculata was >90% on M. lythri and the control diet. H. axyridis larvae reared on G. calmariensis eggs and C. maculata larvae reared on G. calmariensis eggs or larvae did not survive to the adult stage. Preimaginal development times of the three predatory species were 2–5 d longer on G. calmariensis larvae and M. lythri than on the control diets. Adult weights for the three predatory species were significantly reduced when reared on M. lythri and for H. axyridis when reared on G. calmariensis larvae. Myzus lythri is suitable prey for preimaginal survival of the three predatory species. G. calmariensis larvae are highly suitable for development and survival of second-instar to adult C. carnea and less suitable for H. axyridis.