An intelligent species indigenous to Janus IV, it can comfortably live in the airless and dark subterrainan environment. It can also secrete a powerful corrosive which allows the instant fashioning of tunnels for travel. It also has an unusual lifecycle in that every 10,000 years, most of the species dies leaving one female to lay numerous eggs and care for the resulting young.
When the United Federation of Planets set up a mining colony, the Horta tolerated their presence until the miners inadvertantly broke into the egg chamber and, being unaware of their nature, began destroying the eggs. In desperation, the Horta began killing and terrorizing the miners to save her children. The USS Enterprise was sent to investigate the problem and Captain James Kirk and Mr. Spock led the hunt for the creature. Eventually, they made contact with the creature and learned of her grievance. Once fully informed about the situation, they brokered a mutually beneficial arrangement in which the miners treated the Hortas with respect while the creature helped them mine.
In Star Trek fanon, the Horta species eventually acquired a half interest in the mining operations of the planet. Furthermore, least one Horta joined Starfleet and served on the Enterprise under Capt. Kirk where his hardy physique proved a valuable asset.