Slugs are legless, unsegmented and boneless. The head region of a slug has two pairs of retractable tentacles, with one pair bearing eye spots. They are similar to snails, but unlike snails, slugs can live on land without requiring the calcium deposits needed to build shells. Slugs require moist conditions, protection from sun and wind and nourishment to survive.
Slugs are hermaphrodites, having both male and female organs. They are male first, and develop female reproductive organs when fully mature. Each individual slug can lay eggs in batches of 10 to 50 (with a total potential of 300 eggs). They lay the eggs in moist crevices, such as holes in the ground or beneath pieces of wood. Each individual slug has the capacity to produce up to 40,000 offspring in its life.
The eggs of slugs are gelatinous and spherical in shape. They measure approximately 1/8 to 1/4 inch in diameter and are golden or white in color. During warm weather, the eggs will hatch within 10 days. It can take up to 100 days in cooler temperatures (32 to 40 degrees Farenheit). Eggs laid in October or November hatch in the late winter or early spring, when the first warm rain falls.
After an egg hatches, the hatchlings are extremely vulnerable. They are at risk of being eaten by predators, such as toads or ducks. Immature slugs are similar in color to adult slugs. A slug will mature in less than a year.
Most slugs become mature and can begin to reproduce within the first year of their life. They can survive harsh winters if they hide in protected places to keep from freezing. The adult slug ranges in size from 3 to 7 inches. They consume several times their body weight each day, eating a variety of substances, including algae, molds, carrion, centipedes, insects, worms and feces.
Adult slugs can live up to two years. Common causes of death are cold weather, predators and poisoning. Salt will kill them. A slug has a higher percentage of water in their body weight than most animals and insects, and the salt will dehydrate them.