Slugs refer to a loose grouping of invertebrate animals mentioned briefly in the How to Train Your Dragon Book series. Slugs generally refer to terrestrial creatures, but the term Land Slugs is used here to differentiate them from Sea Slugs.
All animals called 'slugs' belong to the Class Gastropoda, but after this grouping slugs are very diverse and are divided into many sub-taxa. Commonly however, slugs can be loosely described as shell-less snails. They are also widely know for producing a sticky 'slime' - mucous that aids in movement, moisture retention, and defense. They are tubular animals without any internal or external skeleton. Because of this they are able to scrunch up or elongate into different conformations. Most slugs have feelers at the head end. One pair almost always has a simple eye at the end. They are able to retract the eyes and feelers into the body if needed.
Slugs consume a wide range of food items, depending on the species. Many eat detritus and organic matter of any kind including plants, lichens, fungi, and even dead animals. Some species are more predatory and even consume other slugs.
In the Book series, slugs are mentioned as a descriptor, particularly for a species of dragon called Squealers.
In reality, something that is very slow can be termed a 'slug' or 'sluggish'. A very few species, such as the Banana slug, are eaten by humans. Some species are also agricultural and garden pests.
|“||They wiggled toward the door like disgusting fat bloated slugs, their nails waving frantically, leaving a trail of snotty slime.||”|
|— Squealers leaving the Great Hall|
Squealer dragons are extremely slug-like in appearance. Norbert the Nutjob has a number of them guarding his frozen father's corpse and the Vegetable-That-Must-Not-Be-Named in the Hysteric Great Hall.