Sources : Opimacus

Leviticus 11:22 (Latin Vulgate version): Comedere debetis, ut est bruchus in genere suo, et attacus atque ophiomachus, ac locusta, singula juxta genus suum. (Thomson translation: These of them in particular you may eat, the brouchus-locust and its species, and the altake-locust and all its species, and the serpent-fighter [ophiomachus] and all its species, and the grasshopper and all its species.)

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Worms 9.31): Opimachus, as the Glossa says, is a worm very small in body, but exceedingly strong in boldness of mind and character. For it is said that it has a battle with snakes and defends its life with skill in fighting; but although it is small in body and unequal to the strength of a snake, yet skill in fighting overcomes its stronger opponent, and it lives securely by boldness rather than by natural strength. - [Badke translation/paraphrase]