Kevin Smith, age 10, of St. Louis, Mo., for his question:

HOW DOES AN EARTHWORM DIG HIS TUNNEL?

Little Pinky has no digging claws, no legs and certainly no shovel. This is enough to make anybody wonder how in the world he digs his burrow down through the dirt. Of all things, he solves the problem by eating. When he digs a new burrow, his small mouth swallows crumbs of dirt, and gradually the tunnel grows deeper. As the dirt goes through his tummy, bits of decaying leaves and other scraps of food are digested. The used dirt comes out of his tail end. It is a neat coil called a worm casting.