Why do worms emerge from the ground in response to vibrations? This was a long-standing mystery with two common explanations. Some people suggested worms might interpret the vibrations as rain and flee to the surface to avoid drowning. Another explanation, orginally proposed by Charles Darwin, was that worms interpret vibrations as the sound of an approaching mole – a major predator for earthworms. Experiments show that Darwin’s idea was correct. There is a very large population of moles living in and around the Appalachicola National Forest, and the worms flee to the surface when a digging mole is present. In contrast, they do not emerge in response to rain.