Slugs Down Garden Services Slugs Slugs and snails are molluscs of the class Gastropoda which means 'stomach foot'.
Gastropods form the second largest class in the animal kingdom, the largest being insects.
Most terrestrial snails and slugs belong to the subclass Pulmonata, order Stylommatophora. There are a few carniverous species. Instead of a shell, slugs have an internal horny plate covering their breathing cavity. There is a range of colours and sizes of slug depending on the species. The Field Slug is 2cm and grey, while the Round Back Slug can be 5-10cm, black or brown and in some cases can have an orange colour on their foot.