Cancer is the fourth sign of the zodiac. Its season runs from June 21-July 22. Cancer is a water sign, and its ruling planet is the moon. Cancer is represented by the crab, which in Greek mythology pinched Heracles while he was fighting the Lernaean hydra. The crab was rewarded by Hera, an enemy of Heracles, by being placed in the heavens. The constellation of Cancer is visible in the Northern Hemisphere in early spring and the Southern Hemisphere in the fall.