Coevolution of pierid butterflies and their cruciferous foodplants IV. Crucifer apparency and Anthocharis cardamines (L.) oviposition.

The oviposition behaviour of the butterfly Anthocharis cardamines has been examined, using the methods of strong inference to investigate foodplant choice. Adaptive explanations for females ovipositing mainly on unshaded, young and large individuals of Alliaria petiolata are rejected in favour of explanations based on 'apparency' to searching females. Floral characters shown to influence intraspecific foodplant apparency are then examined in comparisons between crucifer species, and are shown to explain well the observed deposition of A. cardamines eggs. Cruciferae such as Barbarea vulgaris and Hesperis matronalis, although poor for larval survival, receive many butterfly eggs as a result of large, persistent inflorescences. The contrasting and opposing effects of hostplant apparency and defence are discussed.