Abstract
Most of adult butterflies feed on flower nectar. Certain flower colors are important signals to stimulate their flower-visiting (foraging) behavior. Flower scents also affect its behavior but it remains unclear what components in the scent serve as the releasing factors. When Pieris rapae and Vanessa indica were examined for responses to flower volatiles of certain nectaring plants, several aromatic compounds including phenylacetaldehyde and benzaldehyde strongly stimulated proboscis extension reflex and orientation to artificial models from the butterflies. Such bioactive aromatic compounds are omnipresent as flower volatiles in the plant kingdom, suggesting that butterflies commonly use these olfactory signals for food recognition. On the other hand, several flower volatiles suppress foraging behavior of butterflies, e.g. γ -decalactone present in fragrant olive flowers was identified as a repellent for P. rapae. Several nymphalid butterflies such as Kaniska canace and V. indica feed on tree sap and rotting fruits. Fermentative odors, e.g. ethanol and acetic acid, from these foods evoked their foraging behavior. However, other nymphalid species feeding only on flower nectar never showed positive responses to such odors. These results suggest that butterflies use different olfactory signals depending on their feeding habits.
