Frogs with stumps for legs, extra hind limbs and other malformed body parts are too numerous across North America to be sloughed off as freak accidents. Since ecologists realized the high incidence of amphibian abnormalities in 1995, they have yet to identify the guilty party. However, two suspects have leapt to the forefront: a small parasite that burrows into tadpoles and disrupts leg development, and a pesticide that gets transformed under sunlight into a possible amphibian toxin.