About terrestrial molluscs
There are 124 species of terrestrial molluscs (slugs and snails) in Oregon. Except for the beloved banana slug, most native snails and slugs go unnoticed as they feed on plants, fungi, or an array of decaying organic material. A few are predators. Their alien nature can be fascinating — legless hermaphrodites, love darts, tails that can be lost like a lizard’s, and plenty of mucus.
Due to western Oregon’s fame as excellent slug and snail habitat, most people don’t realize that a huge proportion of our fauna is exotic (mostly introduced from other continents, but a few are from eastern North America). Twenty-eight of Oregon’s species (22%) are exotic, which includes all of our pest species. Of 29 species of slug, 15 are exotic, which is pretty incredible when you consider the concern there would be if over half of our bird species were non-native!
Most people notice slugs and snails when they damage garden plants or because they are large and cross their path. However, there is considerable diversity both in form and behavior of terrestrial molluscs in Oregon. For example, most native species do little or no damage to plants and many are quite small.
Many slugs and snails have a homing behavior. They typically have a refuge to which they return to each day. Most are active at night, although many species can be active on wet, cloudy days.
Slugs and snails are hermaphrodites (they have both male and female genitalia). Some species can even self-fertilize.
During mating, many species use love darts. These are calcium carbonate darts (some are more like spears or arrows) with which they try to stab each other prior to mating. The successful individual (the “stabber”) will typically fertilize more eggs than the “stabbed” mollusc, due to hormones delivered with the dart.