Gray Slug Not Likely to Be Banana Slug

Q: Under a damp rock in my garden in La Canada, I found a huge (4-inch) gray slug. Could it be the famed banana slug that I’ve heard about? Should I worry about having such slugs?

A: First, your slug is probably not a banana slug ( Ariolimax dolichophallus ), since the latter is bright yellow and is thought to confine itself to the central California coast. In Santa Cruz the banana slug is highly regarded, winning overwhelming student approval to continue as UCSC team mascot over the chancellor’s choice, the sea lion. Naturalists in the Santa Cruz area esteem the large slug because it cleans the forest floor and leaves behind a nitrogen-rich fertilizer.

In your garden, though, its diet may include some of your flowers or landscaping plants, so you may not be so enthusiastic about its presence. By the way, the dolichophallus slug did not derive its species name from its color but from its anatomy ( dolicho means “long” in Greek).