Acid spraying, habitat destroying and crab displacing Yellow Crazy Ants have invaded Christmas Island in the Indian Ocean. First detected in the 1930s these aggressive and invasive ants are changing the structure of vegetation on the island and are displacing up to 20 million of the resident crabs on the island by killing them, crowding them out of their normal habitat and by taking over their burrows. Stephen Belcher brings us images of these destructive insects, crabs overcome by ants and the scientists who are taking steps to control the ant supercolonies.