Recently, I found this inch and a half long slug crawling across the living room rug. A slug is basically a snail without a shell. They are very prone to desiccation, and must seek moist spots to prevent drying out.They have two pairs of appendages on the front. The upper pair bears eyespots and senses light. The sense of smell is localized in the lower pair. Slugs are hermaphroditic; they have both male and female sex organs.
Snakes, lizards, frogs, birds and fish all eat slugs. To defend themselves, slugs will contract into a smaller form. They may stick to the substrate quite tenaciously, and their slime may make them difficult to pick up and eat. The slime may also have an unpleasant taste to predators. A few slug species can self-amputate the posterior part of the body, in the hope that the predator will be distracted and eat that part while the main part makes its escape. Slugs are covered with slime and leave a trail of slime behind them as shown in the third photograph. The first photograph shows a small dead insect stuck in the body slime of the slug.
Various types of slugs eat decaying plant material or live plants, fungi, earthworms, or other slugs. Sometimes they are pests because they eat various sorts of ornamental plants or garden crops.