Slugs are familiar pests because of the frequent write-ups they get in gardening publications from eastern U.S. where conditions for slugs are more favorable. Slugs are close relatives of snails, clams and oysters in the phylum Mollusca. These animals have soft, unsegmented bodies that are usually protected by a hard calcareous shell. Slugs look very similar to snails but without the external shell. The shell of a slug is greatly reduced and located internally beneath the fleshy mantle on their backs.
Slugs require a damp environment to survive.
Periodic drying that occurs in Iowa gardens may be one of the factors that limits this animal to relative obscurity except in wet years. Slugs are protected from drying by hiding during the day and feeding at night. They are usually found in the daytime in soil crevices or under boards, rocks, mulch, debris or the foliage of low, dense plants. Both snails and slugs move by gliding on a secretion of mucous or slime. As they move about at night they feed on tender plant parts by rasping large, irregular holes.