Snails and slugs are similar animals. The main difference between them is that a snail has a shell and a slug does not. Along with oysters, clams, and squid, both snails and slugs belong to the group of animals called mollusks. This means that they have a soft body surrounded by a flap of tissue called the mantle. Snails and slugs are further known as gastropods, meaning “belly-footed.” They glide around on a “foot” that moves them forward by expanding and contracting muscles.

Where snails and slugs live

More than 40,000 species, or kinds, of snails and slugs can be found throughout the world. Some live on land or in trees. Others live in freshwater or salt water. Some people include snails in their aquariums.

Land snails and slugs tend to like moist, somewhat warm weather. On hot days a slug may find something to hide under for protection from the sun. A snail may curl up into its shell to keep from drying out. In cold weather snails and slugs may hibernate in the ground.

Snails and slugs that live in water can be found at various depths. Those without gills stay near the water's surface to allow easy breathing, while those with gills live farther down.

Physical features

Snails and slugs are often drab in color, but some tree species can be brightly colored. Some land species in Africa reach a length of 8 inches (20 centimeters), but most snails and slugs are much smaller. Snails have coiled bodies and shells. The shell is made out of a substance produced by the snail's mantle. Therefore the shell can be made larger as the snail grows. A snail's head and foot come out of the front end of the shell. Slugs, which do not have shells, have straight bodies.

Both snails and slugs have eyes located on two long tentacles that stick out from the head. Some snails and slugs also have shorter tentacles that help with the senses of touch and smell.

People often can tell when a snail or slug has been around because of the slimy film that it leaves behind. Snails and slugs produce this fluid to help the foot glide over surfaces. The film hardens as it comes into contact with air.

Behavior and reproduction

Snails generally eat plant material, and slugs may eat dead animal material, plants, or even worms and snails. Snails and slugs themselves are eaten by snakes, toads, turtles, ground beetles, and a variety of birds. When a snail is in danger, it draws its soft body into its shell for protection.

Young are produced in a variety of ways. Some females develop the young inside of their bodies. Others lay eggs in soil or water. Sometimes egg capsules get attached to rocks or plants. Saltwater snails and slugs may produce millions of eggs at a time. These eggs hatch into immature forms called larvae, which can swim by means of vibrating hairs.

Relationship with humans

Many gardeners think of snails and slugs as pests because they eat plants and fruits. They often use poisons to try to rid their gardens of the creatures. Certain types of land snails, however, are eaten by people. Snails are especially popular on menus in France.