Karkinos- Greek CreatureCreature · Monster

The Crab at Lerna

During Heracles's Second Labor, he traveled to the swamps near the spring of Amymone in the Argolid to slay the Lernaean Hydra, a serpent whose venomous breath could kill at a distance and whose severed heads grew back two for one. His nephew Iolaus joined the fight, cauterizing the neck stumps with a burning torch while Heracles hacked. Hera watched the battle with alarm. Seeing that the hero might prevail against the beast she had nurtured, she sent Karkinos — a giant crab lurking in the Lernaean swamp — to intervene.

The crab surfaced from the dark water and clamped its pincers onto Heracles's foot, trying to break his footing while he grappled with the many-headed serpent. Heracles crushed it underfoot without breaking stride. The whole intervention lasted only a moment. Eurystheus later refused to count the Hydra slaying as a valid labor, arguing that Heracles had received help from Iolaus. He made no mention of the crab.

The Constellation Cancer

Hera honored the crab's loyalty by placing it among the stars as the constellation Cancer, a dim grouping between Gemini and Leo. She did the same for the Hydra, and the two mark the Second Labor in the night sky: the monster that nearly killed Heracles and the crab he barely noticed. Hera placed the serpent Draco among the stars for guarding her golden apples, and the crab joined it for a single pinch at a hero's heel.

Greek vase paintings from the sixth and fifth centuries show Karkinos at Heracles's feet during the Hydra fight, a small creature dwarfed by the combat above it. The detail became standard in depictions of the Second Labor.