What is a slug?

   The slug is a terrestrial pulmonate gastropod or snail, in which the shell is represented by an internal horny plate overlying the respiratory cavity. The slugs are chiefly of two families, Limacidae and Arionidae, and most commonly are of the genus Limax. They are vegetable eaters and often ascend trees in search of food and then let themselves down by means of a mucous thread spun from a gland opening on the anterior edge of the foot. In Europe they ravage garden and field crops, but do little damage in the United States. Their general economy is that of the snails. The great gray slug, sometimes 4 inches long, is a European species, introduced into and now become common in eastern North America. A native American slug, which is very common in the United States, is Limax campestris, a small species of slug less than 1 inch long.