130 million years ago, plus or minus a few million, a mollusk evolved to live on land and its shell became the shell forerunner of modern snails. Some of those early snails began to lose their shells and instead developed a whole body slime that is not very different from human mucous though it is poisonous to many animals. These are our familiar west coast banana slugs that grow up to 10 inches long. In the first rains or drizzles of August or September their numbers seem to multiply.

Their slime also enables it to move gracefully, if slowly, over rough rock and sharp blades and climb up glass windows. The copious slime emitted during sex is later eaten to preserve its nutrients. A slug’s penis is also eaten at times. In its habitat the slug’s main purpose is recycling, even if it recycles some of your vegetables before you can do it.