The slug has the characteristics and the body shape that resembles a leech, both have different life habits. leeches have a habit of living in water, and bare snails usually live on land.
How to differentiate and find out whether the animal is a leech or a slug can be done by looking at the head. leech don't have tentacles, while the slug has two pairs of tentacle on the head like a tentacle owned by a snail.
Differences in the nature of both: Leech are parasitic sucking their host blood, while slug often become cultivated plant pests because they eat rotten leaves and micro organisms.
