Butterflies don't have a mouth like you and me, so how do they eat? The butterflies feed upon nectar with their elongated proboscis. The proboscis acts as a tube through which the butterfly sips its food. When they are not eating, the butterfly keeps their proboscis curled up and out of the way. When you are observing your butterflies, keep an eye out to watch them use their proboscis to drink nectar, or from the pieces of fruit you place in their habitat.