Passage 8.34.3
ταύτας τὰς θεάς, ἡνίκα τὸν Ὀρέστην ἔκφρονα ἔμελλον ποιήσειν, φασὶν αὐτῷ φανῆναι μελαίνας· ὡς δὲ ἀπέφαγε τὸν δάκτυλον, τὰς δὲ αὖθις δοκεῖν οἱ λευκὰς εἶναι, καὶ αὐτὸν σωφρονῆσαί τε ἐπὶ τῇ θέᾳ καὶ οὕτω ταῖς μὲν ἐνήγισεν ἀποτρέπων τὸ μήνιμα αὐτῶν, ταῖς δὲ ἔθυσε ταῖς λευκαῖς. ὁμοῦ δὲ αὐταῖς καὶ Χάρισι θύειν νομίζουσι. πρὸς δὲ τῷ χωρίῳ τοῖς Ἄκεσιν ἕτερόν ἐστιν Κουρεῖον ὀνομαζόμενον ἱερόν, ὅτι Ὀρέστης ἐνταῦθα ἐκείρατο τὴν κόμην, ἐπειδὴ ἐντὸς ἐγένετο αὑτοῦ·
These goddesses, they say, appeared black to Orestes when they were about to drive him into madness. But when he had bitten off his finger, they suddenly appeared white again to him, and at the sight of them he regained his sanity. Then he offered sacrifices to the dark ones to avert their anger, and sacrificed also to the white ones. It is customary, moreover, to sacrifice to them at the same time with the Graces. Near the place called Akesai is another sanctuary named Koureion, the "place of haircutting," because there Orestes cut off his hair after he had recovered his reason.