Snakes have no legs. A snake's body is covered with scales, which are made of keratin, the same material as human fingernails. Wide, flat scales on a snake's belly grip the ground like the treads of a tire, which helps the snake move. The most common way snakes move is serpentine movement: the snake bends its body in a series of curves and pushes against surfaces.

In concertina movement a snake coils its body into alternating curves, then straightens out to push itself forward. In rectilinear movement a snake moves forward in a straight line, flexing the skin of its belly. The belly scales are alternately lifted and pulled forward.

In sidewinding, a snake bends in waves both side to side and up and down. Sidewinder rattlesnakes are experts at it. They cross hot desert sand and keep little of the body on the sand at once.

Snakes live on every continent except Antarctica. Some snakes live up in trees. Anacondas spend most of their time in the water. Sea snakes live in the ocean. Blind snakes live underground and eat ants and termites.

Flying snakes flatten their bodies and glide through the air from tree to tree. Five kinds of snakes glide this way, in southern and southeast Asia. A flying snake flattens its body by spreading its ribs, which makes a shape that catches the air. A wild snake is best left alone: it will usually go its own way. If one is near a home, a grown-up can call animal control.

Words to know

• serpentine: curvy movement
• concertina: coil-and-stretch movement
• sidewinding: sideways desert movement
• rectilinear: straight-line movement
• keratin: fingernail material