Pictos was a moon of Vortis. The majority of the Menoptera on Vortis fled there after they were attacked by the Zarbi. The First Doctor told the Animus that the Menoptera were massing on Pictos to counter attack. After their victory the Menoptera decreed that when Pictos pointed to the needle of the kings they would praise the gods for the Doctor and his friends for helping them. (TV: The Web Planet)
Pictos and Vortis' other moons were not native in its star system. They arrived in a very particular order. The Fifth Doctor implied to Nyssa that he was present for their arrival. (AUDIO: Return to the Web Planet)