Sir Richard C. Jebb, Commentary on Sophocles: Oedipus Tyrannus

[1137] ἐξ ἦρος εἰς ἀρκτοῦρον from March to September. In March the herd of Polybus drove his flock up to Cithaeron from Corinth, and met the herd of Laius, who had brought up his flock from the plain of Thebes. For six months they used to consort in the upland glens of Cithaeron; then, in September, when Arcturus began to be visible a little before dawn, they parted, taking their flocks for the winter into homesteads near Corinth and Thebes.

ἀρκτοῦρον （the star α of the constellation Bootes,） first so called in Hes. WD 566 where （610） his appearance as a morning star is the signal for the vintage. Hippoc. Epidem. 1.2.4, has περὶ ἀρκτοῦρον as = “a little before the autumnal equinox ”: and Thuc. 2.78 uses περὶ ἀρκτούρου ἐπιτολάς to denote the same season. See Appendix. ἑκμήνους. Plato （Plat. Laws 916b） ἐντὸς ἑκμήνου, sc. χρόνου: the statement in Lidd. and Scott's Lexicon （t\h ed.） that it is feminine was due to a misunderstanding of the words πλὴν τῆς ἱερᾶς （sc. νόσου） just afterwards. Aristotle also has this form. Cp. ἕκπλεθρος （Eur.）, ἕκπους, ἕκπλευρος. The form ἑξμέδιμνον in Aristoph. Peace 631 is an Atticism: cp. ἕξπουν Plat. Comicus fr. 36, where Meineke quotes Philemon （a grammarian who wrote on the Attic dialect）: Ἀττικῶς μὲν ἕξπουν καὶ ἕξκλινον λέγεται, ὥσπερ καὶ παρὰ Σοφοκλεῖ ἑξπηχυστί: adding Steph. Byz. 345 Ἕξγυιος, πόλις Σικελίας, γραφὴν Ἀττικὴν ἔχουσα. Besides ἔκμηνος, Aristotle uses the form ἑξάμηνος （which occurs in a perhaps interpolated place of Xen. Hell. 2.3.9）; as he has also ἑξάπους. The Attic dialect similarly preferred πεντέπους to πεντάπους, ὀκτώπους to ὀκτάπους, but always said πενταπλοῦς, ἑξαπλοῦς, ὀκταπλοῦς.