In Pelasgian mythology, Arcas (Ἀρκάς) is the son of the god Zeus (the god of thunder and the lord over all gods) and Callisto (the goddess of Ursa Major, the Great Bear). Callisto was a deity of the goddess Artemis. Zeus, being a flirtatious and insatiable god, decided that he wanted her. As she would not be with anyone but Artemis, Zeus cunningly disguised himself as the goddess and seduced her. The child resulting from their union was called Arcas.
Hera (Zeus' wife), became jealous, and in anger, transformed Callisto into a bear. She would have done the same or worse to her son, had Zeus not hid Arcas in an area of Greece that would come to be called Arcadia, in his honor. There Arcas safely lived until one day, during one of the court feasts held by King Lycaon, Arcas was placed upon the burning altar as a sacrifice to the gods. He then said to Zeus "If you think that you are so clever, make your son whole and un-harmed." At this Zeus became enraged. He made Arcas whole and then directed his anger toward Lycaon, turning him into the first werewolf.
After this occurrence, Arcas became the new king of Arcadia, and the country's greatest hunter. One day when Arcas went hunting in the woods, he came across his mother. Seeing her son after so long, she went forth to give him a hug. Not knowing that the bear was his mother, he went to kill her with an arrow. Zeus, taking pity upon the two, decided to avert the tragedy and put them both up in the heavens, and their constellations are now referred to as Ursa Major and Ursa Minor, the big and little bears (also known as the Big and Little Dipper). When Artemis heard of this, she became so angry that she asked Tethys to keep them in a certain place, so that the constellations would never sink below the horizon and receive water.