Hydra

The Hydra is a local monster, tied to the marsh of Lerna in the Argolid. Hesiod names her a child of Typhon and Echidna, reared by Hera as an adversary for Heracles, whose second labour is her killing. The signature detail, that two heads grow for each one severed, is not in Hesiod and enters the tradition later, along with its solution: cauterising each stump with fire while his nephew Iolaus holds the torch. One head was immortal and was buried under a rock, and because Iolaus helped, Eurystheus refused to count the labour. Apollodorus gives the fullest classical summary. The Hydra embodies the motif of a difficulty that multiplies when attacked, and "hydra-headed" survives as a figure for exactly that; the venom Heracles takes from the carcass later kills him in turn, binding the beginning of his labours to his end.

Multi-headed serpents of this general kind are not unique to Greece. Near Eastern art shows comparable monsters centuries before Hesiod, among them a seven-headed serpent depicted on Old Babylonian cylinder seals, and the Ugaritic texts describing Baal's combat with the serpent Litan, discussed elsewhere in this collection under Leviathan, use language of a many-headed sea-monster that some scholars have connected loosely to the same wider Near Eastern imagery. Whether any direct line of influence runs from these older Near Eastern figures to the specifically Argive Hydra of Lerna cannot be shown from the sources, and the safest statement is that the motif of a monstrous, multiplying, many-headed serpent recurs independently across the ancient Mediterranean world rather than spreading from one single point of origin.

The regenerating heads are the whole design of the episode. Cutting is the obvious response and it makes the problem worse, so the solution has to be a change of method rather than more effort. Heracles has his nephew Iolaus sear each stump with a brand as it is cut, and the heads stop returning. The immortal central head is buried under a rock, because it cannot be killed at all and can only be put somewhere.

Eurystheus refused to count the labour. Heracles had accepted help, and the terms did not allow it, so a second labour was set. That refusal is worth noticing: the story goes out of its way to say that the clever solution was against the rules, and the cycle is longer because of it. A crab sent by Hera to bite Heracles during the fight appears in the same passage and is put in the sky as Cancer, which is a second reason the episode stayed in circulation.

The name survived the story. Linnaeus gave the genus Hydra to a small freshwater animal that regrows from fragments, so the classical monster is now a laboratory model for regeneration. Political writing of the early modern period used the hydra for any enemy that multiplies when attacked, and that metaphor is still the most common use of the word in English.