I Googled this to see if it was actually true, and the all-knowing-all-seeing paragon of information that is wikianswers said this:
Earthworms only communicate with each other by touch and taste, but they can feel vibrations, and often avoid predators by sensing their footsteps. They can also sense light and moisture in the air.
To commemorate the discovery of this really quite cozy tidbit of information, I drew two snuggling worms:
Then I drew a very nice cuppa tae: