An Active Sex Life, Even if It Is Sluggish

My recent interest in such neglected or despised species as the bat, the sea slug and the spider has made me something of a spokesman for those who champion such lowly creatures.

Carol Norris of Woodland Hills applauds my paper on the sex life of the sea slug, but notes that if I want to be “truly astonished” I should look into the sex life of the banana slug. For my edification she encloses “The Banana Slug: A Close Look at a Giant Forest Slug of Western North America,” by Alice Bryant Harper (Bay Leaves Press, Aptos, Calif.).

I am indeed astonished. I had no idea that the banana slug existed, though it abounds in the Northern California forests, and I am told it has been adopted as the mascot of UC Santa Cruz. This commendable collegiate choice recalls UC Irvine, which adopted the anteater as its mascot.

Mrs. Harper has studied this animal for years, and has the dubious distinction, as she says, of being called “the banana slug lady.” She concedes that people’s usual reaction is revulsion, but she thinks that is a human problem, and no fault of the slug.

Over the years, Mrs. Harper says, she has watched banana slugs grow from hatchlings to 10-inchers, she has seen them drop from limbs on cords of their own slime, she has seen them eating and being eaten, and she has seen them mating.

Mating is throughout nature a fascinating and sometimes, as in human beings, a comical procedure. But in this field the banana slug is without parallel.

First, though, a word about slime. Though the banana slug is unappealing on several counts, being soft, fat, sluggish and yellow, its ability to make its own slime is undoubtedly among its less endearing traits.

The slug’s body emits a thick, sticky slime that enables the slug to stick to slippery surfaces, even upside down. It also acts as a protective carpet over thorns, gravel or broken glass. The slug leaves a glistening slime trail instead of footprints.

From its tail, the slug produces a slime cord by which it can lower itself from high places. Mrs. Harper says she has seen slugs mating in midair while hanging from their slime cords. Human beings have mated in almost every conceivable environment, but I doubt that any have done it it midair. It’s a challenge.

As for the mating act itself, the banana slug makes the human practice seem unimaginative and dull, as we see it in movies on TV. Like sea slugs, banana slugs are hermaphrodites, which of course doubles the possibilities. They do not, however, fertilize their own eggs, which might result in genetic defects. Quite sensibly, they mate with other banana slugs.

However, when they mate they cross-fertilize, each producing sperm and eggs simultaneously. To begin the mating ritual, two slugs circle each other, nudging, licking and biting, sometimes rather violently, for hours on end. Sometimes hunks of flesh are bitten off.

Then the slugs intertwine in an S position and continue to stimulate each other for hours. When they are tightly together, penetration and exchange of sperm takes place. This may take several hours more.

But it’s not over yet. When they try to separate, the male organ is so distended that it cannot be withdrawn. The slugs twist and turn in grotesque contortions, trying to pull apart.

Finally, utterly frustrated, the slugs give up and take turns gnawing off the recalcitrant organs. This act is known as apophallation . It seems rather a drastic means of controlling overpopulation, but no doubt it works, since the slugs are rendered quite incapable of making love again.

Mrs. Harper describes the conclusion of this mating ritual in a paragraph of rare drama: “In order to separate, these entangled slugs must apophallate. Free at last, after a mating ritual that may last more than 12 hours, the battered and exhausted slugs crawl away. They can now return to their solitary lives. When conditions are favorable, eggs are laid and new banana slugs begin again their distinctive cycle of life.”

Procreation can be cruel. Consider the cecidomyinian gall midges, tiny flies that develop within the mother’s body by parthenogenesis (without male assistance) and devour her from the inside, leaving only a shell.

We humans should consider ourselves lucky.