The Greek goddess Artemis (Diana to the Romans) was a daughter of Leto and Zeus, the supreme god. Her twin brother was Apollo. As the goddess of the hunt, Artemis or Diana is often portrayed with a bow and arrow. She lived in the forest with her companions, the nymphs. Artemis kept strict watch over their chastity, protecting them from the outside world. When the nymph Callisto became pregnant, Artemis changed her into a bear. Artemis also punished unwanted visitors. For example, when the hunter Actaeon spied upon the nymph while they were bathing she turned him into a stag. He was then pursued and torn to pieces by his own hounds, which no longer recognized their master. In art Artemis is usually depicted with a crescent moon on her head because of her traditional identification with Selene, the goddess of the moon.