CACUS, KACUS. Cacus, son of Vulcan, was a fire-breathing, half-human monster. He lived in a cave on the Aventine Hill and preyed on King Evander's subjects. He stole four bulls and many heifers of peerless beauty from Hercules as he drove the cattle of Geryon. Before Hercules could overtake him, the monster had entered his cave and had rolled a huge stone over the entrance. Since he could not remove the stone, Hercules opened up the top of the hill, reached in and caught Cacus, and squeezed him to death in his knotlike grip (Aeneid VIII.194-279). Ovid's account is slightly different. Hercules shoved aside the rock at the mouth of the cave, came face to face with Cacus, then clubbed him four times and killed him (Fasti I.543-586).

Theodulphus, the ninth-century bishop of Orleans, presents Cacus, the bad thief, opposed to Hercules as virtue in his poem, De libris quos legere solebam et qualiter fabulae poetarum a philosophis mystice pertractentur (PL 105: 331-332). Hercules and his labors were important to medieval writers because they saw in him a virtuous man who had conquered great obstacles. The incident with Cacus forms part of the tenth labor, MkT 2107, Bo IV, Metr 7.52-54. [Ercules: Evander]

Cacus appears medially, MkT 2107; Kacus, a spelling variant, occurs in Bo IV, Metr 7.52, 54.