How do earthworms move without legs?
First watch the video, and then read my answer and check out the earthworm activities below.
Earthworms are invertebrates, which means they do not have a backbone. In fact, they don’t have any kind of bones, legs, eyes, or teeth. They feel wet, slimy, and squishy.
While earthworms do not have legs, they do have muscles. They have muscles that circle their body and muscles that go from one end to the other.
The circular muscles allow the worm to make its body wider or more narrow.
The longitudinal muscles can shorten or lengthen the worm’s body.
Using their muscles, earthworms crawl by lengthening its front part and pushing forward through the soil.
Notice how skinny the worm looks when its front end moves forward. Remember that the longitudinal muscles push the worm forward and the circular muscles squeeze the worm’s body inward. Working together, these different muscles move part of the worm forward. When this is happening, tiny bristles called setae on the underside of the worm hold the rear part of the worm in place.
Once the front part has pushed forward, the front setae hold the worm in place and the rear setae turn loose. Now the worm is in position to pull its rear end forward.
Notice how fat the rear end becomes as the worm’s circular muscles relax and its longitudinal muscles contract. The rings of the earthworm expand and contract much like the coils of a slinky.
For fun activities to model the movement of earthworms, see