Why do snakes stick out their tongues?

The old belief that a snake stings with its tongue isn’t true.  The flickering tongue is actually a delicate sense organ that helps the snake to smell.  A snake’s tongue is long and forked at the end.  It darts through a small hole in the front of the snake’s mouth.  

As the snake moves along the ground, its flickering tongue senses odors in the air.  The tongue relays the information to special organs in the mouth which are linked to the snake’s sense of smell.  By picking up the odors, the tongue helps the snake to locate food and sense the presence of enemies. – Dick Rogers