A family visited our school earlier this week, and a child spotted a slug with a very impressive slimy trail!
One reason humans do not much care for slugs is undoubtedly their sliminess. A large Tiger Slug can produce several teaspoonfuls of slime a day.
To us, slug mucous is horrible, but to the slug, this valuable substance is their arms and legs.
Mucous, a watery mixture of various protein, enables slugs to move, by lubricating the space between their bodies and whatever they are touching.
Most importantly, slime forms a protective layer, a soft armour which protects the fragile, water-permeable skin of the mollusc from damage and drying out.
Slug slime comes in two varieties: a thin slippery mucous used to lubricate the slug as it moves, and a thicker type used for a variety of purposes.
Slug slime is not generally toxic but it tastes unpleasant and this may be an effective deterrent against predators, against which such a small, slow animal would have otherwise no defence.
Slug locomotion is one of the triumphs of evolution. To see how it works, place a slug (or a snail, the two groups use an identical technique) on a sheet of glass and observe its muscular 'foot' from underneath.