The Racnoss were wiped out over 4.6 billion years ago by an alliance of civilisations of the time. Insectoid with a half-humanoid, half-arachnid appearance, blood red skin and a crested skull with three pairs of eyes. They had ten razor-tipped limbs, two smaller of which they normally used for manipulation while the rest was mainly used for locomotion. They could produce webbing to wrap up their prey.
They were an aggressive society centered around their queen. Insatiably hungry from the moment of their birth, they consumed everything on the planets they conquered. Their empress was the only survivor of theire civilisation. She hid the ship containing her eggs in suspended animation on the planetesimal that became Earth’s core. She came back to Earth in her Webstar ship on December 24 2006, seeking to use the Huon particles which had been recreated by the Torchwood Institute in the hope of resurrecting her "children" before feasting on the human population of Earth. Here efforts were thwarted and he ship shot by UNIT forces. It remains unknown how she managed to survive for over 4 billion years (some relativistic displacement might be implied) and if her eggs were indeed still viable after all that time (or, for that matter, if the ship containing them had indeed survived the pressures they were subjected to near Earth’s core. Most likely not).
Source: Doctor Who, "The Runaway Bride" (2006).