Passage 2.19.4
ἀρχομένης δὲ ἡμέρας ἐς βοῶν ἀγέλην νεμομένην πρὸ τοῦ τείχους ἐσπίπτει λύκος, προσπεσὼν δὲ ἐμάχετο πρὸς ταῦρον ἡγεμόνα τῶν βοῶν. παρίσταται δὴ τοῖς Ἀργείοις τῷ μὲν Γελάνορα, Δαναὸν δὲ εἰκάσαι τῷ λύκῳ, ὅτι οὔτε τὸ θηρίον τοῦτό ἐστιν ἀνθρώποις σύντροφον οὔτε Δαναός σφισιν ἐς ἐκεῖνο τοῦ χρόνου. ἐπεὶ δὲ τὸν ταῦρον κατειργάσατο ὁ λύκος, διὰ τοῦτο ὁ Δαναὸς ἔσχε τὴν ἀρχήν. οὕτω δὴ νομίζων Ἀπόλλωνα ἐπὶ τὴν ἀγέλην ἐπαγαγεῖν τῶν βοῶν τὸν λύκον, ἱδρύσατο Ἀπόλλωνος ἱερὸν Λυκίου.
At daybreak, a wolf fell upon a herd of cattle grazing near the wall. Having attacked them, it fought against the bull who led the herd. To the Argives it became evident that Gelanor was represented by the bull, and Danaus could be likened to the wolf, since this animal was not friendly toward men, just as Danaus had not been friendly toward them up to that time. When the wolf overcame the bull, for this reason Danaus secured the kingship. Believing therefore that Apollo had sent the wolf against the herd of cattle, Danaus founded a sanctuary for Apollo Lykeios (Apollo of the Wolf).