Spots are like monograms on slugs. Each spotted slug’s spots are unique. A few weeks ago while on slugfari, I came across a slug in the forest that looked like my pet slug (who left the front yard in October and headed toward the forest.) In Photoshop I examined photos of the wild slug and my pet slug side by side.
and a photo of the slug sighted in the forest directly behind our home. After comparing their spots, I determined the forest slug was not my pet slug. But, this little exercise demonstrated the unique coloring of each spotted banana slug.