Commentary Par XXXI 32-33

Callisto was exiled by Diana from the 'nunnery' of chaste forest maidens for her affair with Jove, which resulted in her giving birth to Arcas.  'The "zone" that is always "covered by Helice" is the North.  The nymph Helice or Callisto was transformed into the constellation of the Great Bear, and her son Arcas or Boötes into the Little Bear: [Ovid, Metam. II.496-530, especially 515-517; cf. [Purg XXV 131].  The Bears, or Dippers, are close to the North Star' (DDP Grandgent.Par.XXXI.31-34).