Snail and slug myths, gently untangled

Myth Snails and slugs are insects.

Fact Snails and slugs are gastropods, a kind of mollusc. ‘Gastropod’ means ‘stomach foot’. The Wildlife Trusts: Yellow slug After arthropods (such as insects and spiders), molluscs are the second biggest group of animals on the planet. Natural History Museum, London: For the love of snails and slugs

Myth Slugs don’t have a shell.

Fact A slug still has a shell, but it’s inside, under the thick ‘mantle’ on its back. Natural History Museum, London: For the love of snails and slugs A slug is a gastropod whose shell has shrunk to a small plate or a few grains inside its body, or has gone completely. Britannica: Slug

Myth A gastropod walks on its stomach.

Fact Gastropods glide along on a large foot, but it isn’t really their stomach: in snails, the stomach is tucked away inside the shell. Australian Museum: Snails and slugs

Myth Snails have good eyesight.

Fact Their eyesight is poor: they can only see differences in light and blurry outlines. Natural History Museum, London: For the love of snails and slugs Snails have light-sensitive cells all over their bodies, so they pull back into their shells if a shadow falls on them. Natural History Museum, London: For the love of snails and slugs

Myth Slug blood is red, like ours.

Fact Slug blood is pale blue or grey. Slugs use copper, not iron, to carry oxygen. Royal Horticultural Society: 10 fun facts about slugs (7 March 2024)

Myth Every snail or slug is either male or female.

Fact All slugs and most snails are hermaphrodites: each one is both male and female. Royal Horticultural Society: 10 fun facts about slugs (7 March 2024)

Myth Slime is just water.

Fact Slime works as a glue and stops snails and slugs drying out. It also fights germs. Natural History Museum, London: For the love of snails and slugs Slime acts like a liquid when pushed slowly and like a solid when pushed fast. Natural History Museum, London: For the love of snails and slugs

Myth Most slugs are big garden pests.

Fact Fewer than a quarter of Britain’s slug species are big plant-munchers. Royal Horticultural Society: 10 fun facts about slugs (7 March 2024) Most snails and slugs eat dead and rotting plants, not living ones, so they are important recyclers. Natural History Museum, London: For the love of snails and slugs

Myth Slugs only ever eat plants.

Fact The ghost slug is pure white, almost blind, lives underground and eats earthworms ‘like spaghetti’. Natural History Museum, London: For the love of snails and slugs The shelled slug Testacella has a small flat shell near its tail, lives almost entirely underground and eats worms. Royal Horticultural Society: Who’s who in slugs

Myth Slug pellets only affect slugs.

Fact The Natural History Museum’s mollusc curator suggests not using slug pellets, as they might build up in other animals. Natural History Museum, London: For the love of snails and slugs

Myth All snails and slugs are slow.

Fact The fastest slug is the tramp slug, recorded at 17.6 metres an hour (29.4 cm a minute). Royal Horticultural Society: 10 fun facts about slugs (7 March 2024) · checked 30 Oct 2026