Slugs and Snails (Molluscs)

Molluscs are soft-bodied invertebrates without internal skeletons, although most of them have shells that support and protect their bodies. Molluscs comprise bivalves (clams and mussels) and gastropods (snails and slugs). Gastropod means "belly feet", a reference to the way they move by creeping on their undersides ("bellies").

Slugs have evolved from snails through the reduction or loss of their shell. Lacking a convenient shell to hide in when times get tough, slugs are more susceptible to desiccation than snails, although they protect themselves to some extent with mucus.

Slugs and snails are usually seen as pests in the garden, although most of them prefer to eat decaying plant matter. This means that tidy gardens are likely to suffer more damage than those that have dead vegetation around. However, transfer your molluscs to the compost bin and they will do you a great service there. 

There are about 24 British slug species, and about half of these turn up in the garden from time to time. A mature garden can have an interesting range of snails to try to identify too.  Thrushes, frogs, toads, slow-worms, shrews and hedgehogs all feed on snails and slugs.