Slime probably also has a scent that helps slugs find other slugs. You're most likely to see them at night-March through June and again in October. When you do see a slug, remember that some native species are probably important to our ecosystem. Best known among these is the banana slug. It's also eaten by animals ranging from beetles to raccoons.
Banana slugs get their name because many are bright yellow.
But they can also be white, black, or brown, and may have spots. But the key to banana slug identification is the caudal pore-an indent at the tip of the tail, usually capped with mucous. There are three species of banana slugs, incidentally, of which the type found here is Ariolimax columbianus. When something chomps your marigolds, the culprit is probably not the shy banana slug. More likely it's one of several non-native species, which arrived on bulbs from Holland and Germany or on produce from Europe or the East Coast.