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Spring 2011

Urban Jungle

The changing natural world at our doorsteps | Illustration and text by Patterson Clark      

April 12, 2011

The surprising sex life of leopard slugs

Slug eggs

Gardeners raking away the last tired leaves of winter will often expose clusters of glistening slug eggs, which were laid late last fall. As the weather warms, each tapioca-pearl-sized egg can hatch into a minuscule slug.

For some baby slugs, mom and dad are the same individual: Slugs are hermaphrodites, capable of fertilizing themselves.

But most often, slugs mate with another slug. On warm nights, the common leopard slug, a native of Europe, engages in an elaborate courtship ritual. Two slugs climb to a high spot, where they twist tightly together and lower themselves onto a thread of mucus. While suspended, they twine together their translucent male organs, which emerge from the sides of their heads.

After exchanging sperm, the slugs retract their organs — or chew them off if they can't get them untangled. One slug drops to the ground and the other climbs back up the mucus cord, eating it as it goes.

Both fertilized slugs will lay hundreds of eggs, which also emerge from the sides of their heads. This garden caviar is often consumed by beetles, earwigs, shrews and birds, especially chickens, which will quickly rid a property of slugs and slug eggs.

The fortunate slug that hatches will need to survive for at least two years before it's mature enough to mate.

SOURCES: "The Biology of Terrestrial Molluscs," Lander University, eattheweeds.com, Fairfax County
Public Schools

Leopard Slugs mating


Since thay have little or no shell, slugs secrete much more protective mucus than do snails, but some people see them as unpackaged escargots. However, several factors may give pause to the potential slug chef:

♦ Slugs should never be handled with bare hands, let alone eaten raw. From contact with rat feces, slugs may carry a parasite that can cause a potentially fatal brain disease in humans. Thoroughly cooking a slug — or a snail — should destroy any dangerous parasites.

♦ Slugs are more likely to eat toxic fungi than are snails. Slug harvesters are advised to purge the poison from captive slugs by feeding them grain meal and lettuce for many days before cooking.

♦ Soaking slugs in a vinegar/water solution will kill them and remove much of their mucus, but the cooking water must be changed a couple of times to get rid of all of the slime. The foul-tasting digestive gland in the slug's tail should be removed after cooking.

Bon appetit!