A butterflys tongue.

A butterfly's tongue is called a proboscis. It is a very complex system that is used to ingest the nourishment that the butterfly needs to be able to mate and lay eggs.
The proboscis functions much like a flexible straw, uncoiling when it's ready to sip sweet nectar from a flower. The tongue recoils back into position when not in use.

Here I have been kind enough to photograph a 'proboscis' in action for you.