The Ancients are a very technologically advanced insectoid species from another universe which developed a hive based civilisation and wormhole-based technology. Thin and bipedal and brown skinned, they have four arms, two shorter upper arms, and two longer arms that are lower on their torso. The upper arms end in lobster-like claws while the lower arms appear to have three-fingered hands. They also have several shorter tentacle-like appendages both around and on their facial area. Shapeshifters, they can alter their appearance to look like members of the species they interact with.
Using wormholes as bridges to our universe, they modified several members of their own species, so that they could live among species of our universe with the task to catalogue, report, and influence their activities.
When their planet became unable to sustin them, they started to look for a new world to establish themselves in our universe. They abducted a human to see if hey could cohabit with humanity on Earth but their experiment ended up with negative results. They soon after found a suitable planet.
Source: Farscape Universe