From Augustine’s City of God XVIII.17
“Varro adds to this by relating other things no less incredible about that most renowned witch Circe, who changed the companions of Ulysses into beasts, and about the Arcadians, who after drawing lots would swim across a certain pool and there be turned into wolves; they would then live with similar wild beasts in the deserts of that region. If, however, after nine years they had not tasted of human flesh, they would be turned back into humans if they swam back across the pond. He also mentions that a certain Demaenetus had tasted a part of the sacrifice in the form of a burnt boy which the Arcadians used to offer to their god Lycaeus; he was turned into a wolf and after ten years restored to his human form. He then practiced boxing and won that contest in the Olympics. The same historian thinks that such a name was not given to Pan Lycaeus and Jupiter Lycaeus for any other reason than this transformation into wolves, which they used to think could not happen but by divine influence. (For, a wolf is called a lykos in Greek, from which it appears that the name of Lycaeus is derived. He also says that the Romans were called Luperci as though derived from the seed of those mystery rites.)”
Hoc Varro ut astruat, commemorat alia non minus incredibilia de illa maga famosissima Circe, quae socios quoque Vlixis mutauit in bestias, et de Arcadibus, qui sorte ducti tranabant quoddam stagnum atque ibi conuertebantur in lupos et cum similibus feris per illius regionis deserta uiuebant. Si autem carne non uescerentur humana, rursus post nouem annos eodem renatato stagno reformabantur in homines. Denique etiam nominatim expressit quendam Demaenetum gustasse de sacrificio, quod Arcades immolato puero deo suo Lycaeo facere solerent, et in lupum fuisse mutatum et anno decimo in figuram propriam restitutum pugilatum sese exercuisse et Olympiaco uicisse certamine. Nec idem propter aliud arbitratur historicus in Arcadia tale nomen adfictum Pani Lycaeo et Ioui Lycaeo nisi propter hanc in lupos hominum mutationem, quod eam nisi ui diuina fieri non putarent. Lupus enim Graece *lu/kos dicitur, unde Lycaei nomen apparet inflexum. Romanos etiam Lupercos ex illorum mysteriorum ueluti semine dicit exortos.