Lewis & Short

Myrmĭdŏnes, um, m., = Μυρμιδόνες, the Myrmidons, a people of Phthiotis (Thessaly), about Phthia and Larissa Cremaste, under the sway of Achilles, Enn. ap. Non. 472, 27 (Trag. v. 222 Vahl.); Verg. A. 2, 7; Ov. M. 7, 654.
In sing. also as fem.: cruentae Vulnere Myrmidonis, Stat. Th. 5, 223.