The following fragment of Pherecydes, the fifth century mythographer, is from a Scholion to Euripides’ Phoenissae 53. Fowler (Early Greek Mythography, 2001) prints this as Pherecydes fr. 95):
“Pherecydes says these things about the children and the marriages of Oedipus: “Kreon,” he says, “gave the kingdom and Laios’ wife, his own mother Iokasta to Oedipus, and from here were born Phrastôr and Laonutos, who died thanks to the Minyans and Erginos. Then a year had passed, Oedipus married Euryganeia, the daughter of Periphas, and from her were born Antigone and Ismene, the girl Tydeus took at the stream and for that reason the stream is called Ismene. The sons Eteokles and Polyneices were also born to Oedipus from here. When Euryganeia died, Oedipus married Astymedea, the daughter of Stenelos. And some people add that Euryganeia was the sister of Oedipus’ mother Iokaste.”
γαμεῖ δὲ τὴν τεκοῦσαν: Φερεκύδης τὰ κατὰ τοὺς Οἰδίποδος παῖδας καὶ τὰς γημαμένας οὕτως ἱστορεῖ· ‘Οἰδίποδι, φησὶ, Κρέων δίδωσι τὴν βασιλείαν καὶ τὴν γυναῖκα Λαΐου, μητέρα δ’ αὐτοῦ ᾿Ιοκάστην, ἐξ ἧς γίνονται αὐτῷ Φράστωρ καὶ Λαόνυτος, οἳ θνῄσκουσιν ὑπὸ Μινυῶν καὶ ᾿Εργίνου. ἐπεὶ δὲ ἐνιαυτὸς παρῆλθε, γαμεῖ ὁ Οἰδίπους Εὐρυγάνειαν τὴν Περίφαντος, ἐξ ἧς γίνονται αὐτῷ ᾿Αντιγόνη καὶ ᾿Ισμήνη, ἣν ἀναιρεῖ Τυδεὺς ἐπὶ κρήνης καὶ ἀπ’ αὐτῆς ἡ κρήνη ᾿Ισμήνη καλεῖται. υἱοὶ δὲ αὐτῷ ἐξ αὐτῆς ᾿Ετεοκλῆς καὶ Πολυνείκης. ἐπεὶ δὲ Εὐρυγάνεια ἐτελεύτησε, γαμεῖ ὁ Οἰδίπους ᾿Αστυμέδουσαν τὴν Σθενέλου.’ τινὲς δὲ Εὐρυγάνειαν ἀδελφὴν λέγουσιν εἶναι ᾿Ιοκάστης τῆς μητρὸς Οἰδίποδος: —
In Greek myth, there are at times conflicts between fathers and sons when there are new wives (consider Theseus and Hippolytus) or there are dynastic struggles (or even murder: consider Chrysippus) when there are sons from multiple women. In part, the complex genealogy in this passage may be directly or indirectly connected to the strife that ensues between Oedipus and his sons (causing him to curse them) leading to the Seven Against Thebes. The deaths of the first sets of sons may be reflexes of Greek intergenerational myths or somehow related to the theme of internecine strife that becomes dominant at Thebes.
Within this theme of strife, we need to also figure out what is going on with the tale of the Minyans and Erginos. Minyas was a legendary founder of the Boiotian city of Orchomenos which was important in the Early Archaic period. These are figures from other Boiotian cities who seem, in this tale, to have killed the first sons of Oedipus. In myth, they attack Thebes, and Erginos, King of the Minyans, exacts a tribute for the death of his father. Pherecydes has somehow condensed this myth into the story of Oedipus and also failed to mention the most famous part: that Herakles returns to Thebes and forces Orchomenos to pay tribute, perhaps even burning the palace. But this account, obviously doesn’t square with the explanation that Pherecydes is seeking here.
Oedipus’ marriages are also interesting. Most students are surprised to learn he is often given two wives (Iocaste and Euryganeia). Here, he gets a third, Astumedea. Note the marriage between Oedipus and the daughter of Sthenelos. This is strange, considering the fact that Stenelos helps to sack Thebes (if this is the same Sthenelos who is a companion of Diomedes in the Iliad). And, third, just in case you missed it: this tradition has Oedipus marked out for committing incest with two family members: his mother and his aunt.
Pherecydes’ fragment also highlights the extent to which local heroic traditions could be submerged and then integrated into Panhellenic myths. Erginos seems to be a local hero of Boiotia, specifically Orchomenos. According to Pausanias (9.37) after his father Klumenos was killed while celebrating a festival to Poseidon at Thebes, he attached the city and imposed a yearly indemnity of 100 oxen. This narrative is similar to the tale of Minos’ indemnity on Athens for the death of his son. And, similarly, a city-hero returns to set things right.
When Herakles returns, he attacks Orchomenos. According to Eustathius (Comm. Ad Il. II.417), Herakles kills Erginos. According to Pausanias, Erginos makes peace with Herakles. According to Apollodorus (2.67) when Herakles returns to Thebes he disfigures the heralds of Orchomenos who come for the tribute by cutting off their ears and noses. After this, he kills Erginos. Diodorus Siculus records much of the same tale and has Creon awarding his daughter Megara to Herakles in gratitude for his service to the city (4.40). Whatever the details of the death of Erginos, the story asserts the preeminence of Thebes over the ancient city of Orchomenos.
Apollodorus’ account does not leave room for the rest of Erginos’ tale. He appears among the Argonauts where he takes the rudder after the death of Tiphous (Schol. In Ap. Rhodes 193.12) and according to Pausanias he had children late in wife after consulting the oracle at Delphi and taking a young wife.
Erginos’ children were Agamedês and Trophonios who appear in the Homeric Hymn to Apollo laying the first stone for his temple (λάϊνον οὐδὸν ἔθηκε Τροφώνιος ἠδ’ ᾿Αγαμήδης / υἱέες ᾿Εργίνου, φίλοι ἀθανάτοισι θεοῖσιν, 296-297). But this did not turn out as well as one might think. According to a spurious dialogue attributed to Plato (Steph. 367c1-3), the two boasted during the construction that the temple would be strongest because of them—then they died in their sleep. But Eriginos had other children, and the leaders of the contingent from Orchomenos—Askalaphos and Ialmenos—are his descendents (Οἳ δ’ ᾿Ασπληδόνα ναῖον ἰδ’ ᾿Ορχομενὸν Μινύειον / τῶν ἦρχ’ ᾿Ασκάλαφος καὶ ᾿Ιάλμενος υἷες ῎Αρηος Il. 2.511-512).
The last part of his tale worth mentioning appears in two Scholia to Pindar (Schol. In Pindar O4 29d6; and Schol in Pind. O4 31c7). When Erginos was an old man he went to compete in the funeral games for Thoas. The crowd laughed at him because of his age and he showed them by winning the race in full armor.