Chemical Recognition of Host Plants for Oviposition by the Cabbage Butterfly, Pieris rapae (Lepidoptera: Pieridae)

A bioassay using green index cards demonstrated the stimulatory effect of cabbage extracts on oviposition by Pieris rapae. The chemicals involved are water soluble, and the butterflies readily differentiated between different concentrations. High concentrations of the glucosinolate sinigrin also stimulated oviposition but had little effect on the spatial distribution of eggs over treated and control areas of cards. Response to cabbage extracts, however, resulted in precise discrimination between treated and control areas throughout the active life of the butterflies. Cabbage volatiles did not enhance stimulation of oviposition on extract-treated cards. The results suggest that more than one nonvolatile chemical is needed for both stimulation of oviposition and selection of the exact oviposition site