The suitability of several Cruciferae species for the survival and development of the larvae of Anthocharis cardamines, which are seed and flower predators, was investigated. Large differences, consistent in time and space, were observed between the survival of sub-populations on different hostplants. Foodplants influenced A. cardamines survival and development by allelochemical and mechanical defences, which may also weaken a larva against pathogen attack. Oviposition by females appeared surprisingly maladaptive however with proportionately most eggs being laid on the hostplants yielding poorest larval survival, in opposition to previous expectations of coevolutionary theory. The evolutionary consequences of butterfly predation for Cruciferae are discussed, and juxtaposed to the needs of pollination.