Andromeda Gamma Epsilon

The Breeding Colonies were a group of worlds in the Andromeda Galaxy which were 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. (DW: The Ark in Space)