Slug slime is a watery mixture containing numerous proteins which allows slugs to crawl. The slime lubricates or greases the area between the slug and the surface on which it moves. This sticky, seemingly gross substance is vital to a slug, as it acts as the slug’s arms and legs. The slime also serves as a protective cover to the slug’s fragile skin—it prevents the skin from damaging and becoming overly dry.
A slug’s slime actually prevents stickiness. It ensures that debris, such as leaves and dirt, does not stick to its body. The slug leaves it all behind, along with its slime.
The stickiness of the slime does become enhanced, however, when a slug is either injured or bothered. This may be why, if one steps barefoot on a slug, the slime sticks to the bottom of the foot for a long time.
There are actually two kinds of slug slime: a thin, slippery kind used to help the slug as it moves, and a thicker kind used for various reasons. The slime isn’t toxic, but this doesn’t mean it tastes good. The awful taste helps the slow-moving animal be protected against predators.
If you find slug slime on your sidewalk or porch, do not apply water, as this makes the problem worse. Instead use a paper towel soaked in white vinegar to remove the slime. The white vinegar will help it to dissipate.