ARTEMIS (Roman Diana) Twin sister of Apollo, an eternally virgin huntress who haunts wild places. She is sometimes referred to as Potnia Theron (Mistress of the Beasts) indicating her concern for and power over wild animals. She is also concerned with women's transition from girlhood to adulthood (via marriage) and with childbirth, a concern she shares with Hera and Eileithyia. Women who die are said to be struck down by her arrows. Euripides' Hippolytus shows her in opposition to Aphrodite. Actaeon and Hippolytos are two young men who, in different ways, are destroyed by their association with Artemis. Artemis demands the sacrifice of the virgin Iphigeneia at Aulis before she will allow the Greek fleet to sail against Troy. The reasons given for her anger vary: Agamemnon kills a deer in her sacred grove (mentioned in Sophocles, Electra); or he boasts that he is a better shot than Artemis herself (Apollodorus). For the motif of Artemis' concern to protect her animals against marauding heroes see the story of Heracles and the Kerynitian hind; for the motif of mortals boasting of their superiority to the gods see the stories of Arachne, Actaeon, Marsyas, Niobe, the Lesser Ajax. Kallisto was one of Artemis' nymphs who offended the goddess by becoming pregnant by Zeus and was banished. The jealous Hera then further punished her by turning her into a bear. The stories of Actaeon and Kallisto were known in the Renaissance through Ovid's Metamorphoses and were popular subjects for artists.