Earthworms do not have eyes or ears, but they have a mouth and are sensitive to heat, light, and touch. The earthworm's body is made up of segments. On each segment, except the first and last, are four pairs of tiny bristles called setae that help the worm move through the earth. A worm crawls by lengthening its front part and pushing through the soil, then pulling the hind part up. A worm's body wall has two kinds of muscles that it uses to crawl.
Circular muscles surround the worm's body and can make the body shrink or spread out.
Longitudinal muscles run the length of the body and can shorten or lengthen the worm. The earthworm has no lungs or gills. It breathes through its thin skin, which is in contact with the air between the particles of soil. When it rains, these air spaces fill with water, and earthworms then must either come to the surface or drown. If the weather becomes too dry and warm, a worm will die.