In discussing tales of Diomedes’ companions being turned into birds, Augustine in De Civitate Dei (City of God) discusses werewolves (18.17, the full text):
“In order to make this seem more likely, Varro reports other fantastic tales concerning the infamous witch Circe, who transformed Odysseus’ companions into beasts, and concerning the Arcadians, who were by chance transformed when they swam across a certain lake in which they were turned into wolves. Then, they lived as wolves in the same region. If they did not eat human flesh, then they would be returned to human form after swimming across the same lake again.
And he also specifies that a certain Demanaetus tasted of the sacrifice which the Arcadians used to make to the Lycaean god, after the child was burned on the altar, and that he transformed into a wolf and, once he became a man again, competing in boxing at the Olympian games and achieved a victory. Varro does not believe for this reason that Pan or Jupiter were given the name “Lykaios” in Arcadia for any other reason than their ability to turn men into wolves, since they did not believe that this could happen except through divine power. As you know, a wolf is called lykos in Greek, and this is where the name Lykaian comes from. Varro adds that the Roman Luperci arose from their own mysteries similarly.
But what can we who talk about these things say about this kind of deceit by the devil’s forces?”
Augustine goes on to object to these tales and discuss Apuleius’ Golden Ass. I started translating this, but it is a bit of a Halloween buzzkill..
[XVII] 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.
Sed de ista tanta ludificatione daemonum nos quid dicamus…