Identification of Slugs

The term "slug" refers only to the body shape adopted by a shell-less (or nearly so) mollusc. Detailed study of their anatomy reveals that they have evolved several times from different ancestors. They are not a natural group of closely related animals. Some slugs are more closely related to certain snails than they are to each other

A saddle-like mantle extends over the anterior part of the back of the slug, and this bears a "breathing hole", or pneumostome. If you cannot see a mantle or a pneumostome on your specimen, have a look at the hind end and make sure it does not carry a tiny plate-like shell. If it does,  you may have Testacella, so click here.

If you can see a pneumostome on the mantle, click on the image below.