Anagrus mutansWalker andAnagrus silwoodensisWalker overwinter as late second instars inside eggs ofCicadella viridisL. (Homoptera: Cicadellidae).Dicranotopis hamata(Boheman) (Homoptera: Delphacidae) is a summer host of both parasitoid species. Parasitoid size and fecundity were greater in females reared fromC. viridis(the larger host) than in those reared fromD. hamata.SmallA. mutansfemales failed to produce progeny onC. viridis.Progeny reared fromC. viridiswere larger than those fromD. hamata. A. mutansdeveloped faster inD. hamataeggs, whereasA. silwoodensisdeveloped faster inC. viridiseggs.