(Ἕρμαρχος), sometimes, but incorrectly, written IIermachus. He was a son of Agemarchus, a poor man of Mytilene, and was at first brought up as a rhetorician, but afterwards became a faithful disciple of Epicurus, who left to him his garden, and appointed him his successor as the head of his school, about B. C. 270. (D. L. 10.17, 24.) He died in the house of Lysias at an advanced age, and left behind him the reputation of a great philosopher. Cicero (de Fin. 2.30) has preserved a letter of Epicurus addressed to him. Hermarchus was the author of several works, which are characterised by Diogenes Laertius (10.24) as κάλλιστα, viz. Ἐπιστολικὰ περὶ Ἐμπεδοκλέους, in 22 books, Περὶ τῶν μαθημάτων, Πρὸς Πλάτωνα, and Πρὸς Ἀριστοτέλην; but all of them are lost, and we know nothing about them but their titles. But from an expression of Cicero (de Nat. Deor. 1.33), we may infer that his works were of a polemical nature, and directed against the philosophy of Plato and Aristotle, and on Empedocles. (Comp. Cic. Ac. 2.30; Athen. 13.588; Phot. Bibl. Cod. 167, p. 115b. ed. Bekker.) It should be remarked that his name was formerly written Hermachus, until it was corrected by Villoison in his ii. pp. 159, 290.