Yellow Cellar Slug
Yellow cellar slugs are an introduced species, and reaching over four inches long at maturity they are the largest slugs in the area. They are mottled with yellow and gray and their antennae are a gray-blue color. These slugs also produce a very sticky yellow mucus. The green cellar slug (L. maculatus) may also be found here, but dissection would be needed to confirm it.
Photo Credit: Thomas Everest