That is, the "bullkillers," are according to the earliest accounts a race of men who inhabited the mountains and forests of Thessaly. They are described as leading a rude and savage life, occasionally carrying off the women of their neighbours, as covered with hair and ranging over their mountains like animals. But they were not altogether unacquainted with the useful arts, as in the case of Cheiron. (Hom. Il. i. 268, ii. 743, in which passages they are called phêres, that is, thêres, Od. xxi. 295, &c.; Hesiod. Scut. Herc. 104, &c.) Now, in these earliest accounts, the centaurs appear merely as a sort of gigantic, savage, or animal-like beings; whereas, in later writers, they are described as monsters (hippocentaurs), whose bodies were partly human and partly those of horses. This strange mixture of the human form with that of a horse is accounted for, in the later traditions, by the history of their origin. Ixion, it is said, begot by a cloud Centaurus, a being hated by gods and men, who begot the hippocentaurs on mount Pelion, by mixing with Magnesian mares. (Pind. Pyth. ii. 80, &c.) According to Diodorus (iv. 69; comp. Hygin. Fab. 33), the centaurs were the sons of Ixion himself by a cloud; they were brought up by the nymphs of Pelion, and begot the Hippocentaurs by mares. Others again relate, that the centaurs were the offspring of Ixion and his mares; or that Zeus, metamorphosed into a horse, begot them by Dia, the wife of Ixion. (Serv. ad Aen. viii. 293; Nonn. Dionys. xvi. 240, xiv. 193.) From these accounts it appears, that the ancient centaurs and the later hippocentaurs were two distinct classes of beings, although the name of centaurs is applied to both by ancient as well as modern writers.
The Centaurs are particularly celebrated in ancient story for their fight with the Lapithae, which arose at the marriage-feast of Peirithous, and the subject of which was extensively used by ancient poets and artists. This fight is sometimes put in connexion with a combat of Heracles with the centaurs. (Apollod. ii. 5. § 4; Diod. iv. 12; Eurip. Herc. fur. 181, &c.; Soph. Trachin. 1095; Nonn. Dionys. xiv. 367; Ov. Met. xii. 210, &c.; Virg. Georg. ii. 455.) The scene of the contest is placed by some in Thessaly, and by others in Arcadia. It ended by the centaurs being expelled from their country, and taking refuge on mount Pindus, on the frontiers of Epeirus. Cheiron is the most celebrated among the centaurs. [CHEIRON.]
As regards the origin of the notion respecting the centaurs, we must remember, in the first place, that bull-hunting on horseback was a national custom in Thessaly (Schol. ad Pind. p. 31.9, ed. Boeckh), and, secondly, that the Thessalians in early times spent the greater part of their lives on horseback. It is therefore not improbable that the Thessalian mountaineers may at some early period have made upon their neighbouring tribes the same impression as the Spaniards did upon the Mexicans, namely, that horse and man were one being. The centaurs were frequently represented in ancient works of art, and it is here that the idea of then is most fully developed. There are two forms in which the centaurs were represented in works of art. In the first they appear as men down to their legs and feet, but the hind part consists of the body, tail, and hind legs of a horse (Paus. v. 19. § 2); the second form, which was probably not used before the time of Phidias and Alcamenes, represents the centaurs as men from the head to the loins, and the remainder is the body of a horse with its four feet and tail. (Paus. v. 10. § 2; Plin. H. N. xxxvi. 4.) It is probably owing to the resemblance between the nature of the centaurs and that of the satyrs, that the former were in later times drawn into the sphere of Dionysiac beings; but here they appear no longer as savage monsters, but as tamed by the power of the god. They either draw the chariot of the god, and play the horn or lyre, or they appear in the train of Dionysus, among the Satyrs, Fauns (Panes), Nymphs, Erotes, and Bacchantes. It is remarkable that there were also female centaurs, who are said to have been of great beauty. (Philostr. Icon. ii. 3.)