The Archernarians were natives to Archernar IV, a huge ancient space station. They evolved millions of years ago after the giants, known as divine builders, that were on the station abandoned it, leaving its life support system on. They along with the other insects evolved into sentient beings, developing a unique culture and science.
In the 2260s, the Archernarians started to run experimental warp flights to a neighboring star system. This made them prime candidates for contact with the United Federation of Planets. Contact was made with the Federation when Captains James T. Kirk and Elizabeth Cassady made first contact with them. In 2270, the Archernarians were to become part the Federation. However, after a brief coup and an uprising by the Crawlers, they then decided to return to the builders' dimension, leaving the galaxy.(TOS comic: "Mission's End")