A few species of slugs are pests of agriculture and can destroy foliage faster than plants can grow.
Most garden slugs, however, eat dead leaves, fungus, and decaying plant material.
Some slugs are predators and eat earthworms, snails, and even other slugs.
It may surprise someone whose vegetable garden has been munched by voracious shell-impaired land snails, but slugs do have some fans.
Among them are their predators, like snakes, toads and starlings, another pest. Some slugs are edible by humans, too.
Most of the worst garden pests are foreign invaders.
Domestic varieties like the nine-inch banana slug (Ariolimax columbianus) of the Pacific Northwest content themselves with fungi and decaying vegetable matter in the woods.
They were part of the diet of Indians and of early German immigrants, who batter-fried them.
And at least one scientist, Dr. Alan Gelperin, a research scientist at Sell Labs in Murray Hill, New Jersey, found slugs to be excellent guinea pigs.
He used the brains of slugs in his research on the neural mechanisms of learning.