Thuridilla kathae is a tiny little sapsucker that resembles a few other Elysias and Thuridillas, so make sure you haven’t found a Thuridilla carlsoni, an Elysia degeneri, or Elysia lobata .  This little one (1/2 inch or 12 mm maximum)  was found in 1 metre or 3 ft of water in amongst the rocks and algae in the shallow protected area of the Koʻieʻie Loko Iʻa Fishpond, North Kihei, Maui.   For more information and photos check out Sea Slugs of Hawaii.  Cory Pittman, one of the authors of the site, was the first to record this species on Hawaii in 1989.