Two species of paropsine chrysomelid defoliators of eucalypts, Chrysophtharta bimaculata (Olivier). and C. agricola (Chapuis), showed distinct host preferences to a Monocalyptus species, Eucalyptus delegatensis R. T. Bak., and a Symphyomyrtus species, E. dalrympleana Maiden, respectively in mixed regeneration stand. Females of each species showed strong ovipositional host preference in a cage trial. Larvae of both species achieved a faster rate of consumption and matured more rapidly on foliage of E. delegatensis than on E. dalrympleana, but C. bimaculata was faster than C. agricola. On E. dalrympleana, C. agricola was more rapid than C. bimaculata. Findings are discussed in relation to ecological strategies employed by these species.