Hercules and the Hydra
King Eurystheus then told Hercules he had to go kill the Hydra for another one of his labors. The Hydra was a huge snake with seven heads. Hercules thought, "Well, that sounds easy. I'll just go cut off its heads with my sword." But when he was fighting the Hydra, he realized that whenever he cut off a head, two more grew back out of the neck! By fighting the Hydra, Hercules was only making it stronger.
So Hercules (with his nephew's help) thought of another plan. Whenever Hercules cut off a head, his nephew burned the stumps with fire. Then the heads did not grow back, and so Hercules was able to kill the Hydra.
This is a video telling the story of Hercules' second labor.
(Hercules is an enemy of Hera, and Hera is an Earth goddess, and earth goddesses are always associated with snakes, that crawl on the earth).
Learn by doing: handle some snakes (at a pet store?)
More about Hercules
Twelve Labors of Hercules (Step into Reading, Step 3), by Marc Cerasini. Very easy, for beginning readers.
The Story of Hercules (Dover Children's Thrift Classics), by Robert Blaisdell (1997). , very cheap.
Hercules, by Nancy Loewen (1999). Still for kids, but more sophisticated, with a look at how the myth was passed on and what it meant to people, as well as the story itself.
D'aulaire's Book of Greek Myths, by Edgar and Ingri D'Aulaire. (Look under Heracles).
The Myths of Herakles in Ancient Greece, by Mark W. Padilla (1998). By a specialist, for adults.