The Breeding Colonies were a group of planets in the Andromeda Galaxy controlled by the Wirrn. Though the Wirrn lived most of their life in space, they needed terrestrial planets to reproduce so they could incubate animals — usually senseless herbivores — limiting their technological progress. When humans expanded into Andromeda they started taking the breeding planets and, after a thousand years of fighting, eventually drove the Wirrn from the galaxy. (TV: The Ark in Space)