A butterfly’s sense of taste is coordinated by chemoreceptors on the tarsi, which work only on contact, and are used to determine whether an egg-laying insect’s offspring will be able to feed on a leaf before eggs are laid on it.
They have taste sensors on their feet, and by standing on a leaf, they can taste it to see if their caterpillars can eat it. Most adult butterflies can’t bite or chew.
They don’t have mouths that allow them to bite or chew, instead they have a long straw-like structure called a proboscis which they use to drink nectar and juices. But the proboscis doesn’t have any taste sensors.