LSJ
contr. Ἡρακλῆς, ὁ, the former in Ep., Pi., Hdt., and E. Heracl. 210, Ion 1144, HF 924; the latter also in E., S., and Att. Prose; the orig. forms of the obl. cases Ἡρακλέεος, κλέεϊ, -κλέεα nowhere appear in use; but in Att. the contracted forms Ἡρακλέους Ar. Nu. 1050, Ἡρακλέει E. Heracl. 8, 988, Ar. Av. 567, Ἡρακλέα Id. V. 757 (anap.) (also in h.Hom. 15.1, Hes. Sc. 448, Theoc. 24.1); in Ion. and Ep., Ἡρακλῆος, κλῆϊ, -κλῆα (-κλῆϊ Pi. I. 5 (4).37, -κλῆος dub. in E. Heracl. 541); — these forms are still further shortd., Ἡρακλέος Hdt. 2.42 (v.l. -έους), Pi. O. 3.44 (scanned – ˘ – P. 10.3), E. HF 806 (lyr.), Ἡρακλέῖ Hdt. 2.145, Theoc. 25.71; Ἡρακλέα Hdt. 2.42 sq., Pi. O. 10 (11).16, AP 9.391 (Diotim. or Call.) (scanned – ˘ – S. Tr. 233, Ar. Th. 26); again contr. Ἡρακλῆ S. Tr. 476 cod. A, interpol. in Pl. Phd. 89c, Ael. VH 1.24; Ἡρακλεῖ B. 8.9, Th. 7.73; irreg. acc. Ἡρακλέην A.R. 2.767, dub.l. in Theoc. 13.73; contr. Ἡρακλῆν v.l. in Paus. 8.31.3 and Epigr. ap. Alcid. Od. 24, BGU 166.12 (ii AD); voc. Ἡράκλεες Archil. 119, Pi. N. 7.86, E. HF 175; Att. Ἡράκλεις Pl. Euthd. 303a, etc., later Ἥρακλες Orph. H. 12.1 [α], AP 9.468 [α], Gramm. ap. Lib. Ep. 255; pl. Ἡρακλέες Pl. Tht. 169b (but Ἡρακλεῖς Hdn. Gr. 1.424), acc. -έας Ar. Pax 741; dual Ηρακλέε Philostr. VA 5.5; (< Ἥρα, κλέος):
Heracles, Il. 14.266, etc. ; Ἡρακλέος στᾶλαι (v. Ἡράκλειος), prov. of going to the farthest point, Pi. O. 3.44; Ἡρακλέους ὀργήν τιν’ ἔχων a temper like Heracles, Ar. V. 1030, Pax 752; prov. of close friendship, ἄλλος Ἡρακλῆς, ἄλλος αὐτός (Mss. οὗτος) Arist. EE 1245a30; but ἄλλος οὗτος Ἡρακλῆς ΄a second Heracles΄, Id. MM 1213a13, Varr. Sat. Men. tit. ; voc. Ἡράκλεις as an exclamation of surprise, anger, or disgust, Ar. Ach. 284, Nu. 184.
the planet Mars, Arist. Mu. 392a25, Ach.Tat. Intr. Arat. 17. [α, long by position in Ep. and E., as Heracl. 123.]
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)