Arachnae was the designation of an Class M planet in the Arachnae system. It was the home of the Arachnians. At some point after Stardate 6454.5, this planet drifted into the Neutral Zone and into Romulan space. Starfleet attempted to convince the local people to join the United Federation of Planets, but were attacked for their trouble. Arachnae had small, shallow oceans, narrow rivers, and little rainfall. It was roughly the size of Earth. This planet was also home to a species very similar to the Horta, but not as intelligent. (TOS novel: Vulcan!)