Tusock or Tussock: How To spell?

The word Tusock is misspelled against Tussock, a noun meaning "A caterpillar of any one of numerous species of bombycid moths. The body of these caterpillars is covered with hairs which form long tufts or brushes. Some species are very injurious to shade and fruit trees. Called also tussock caterpillar. See Orgyia."