Before the birth of modern insecticides, farmers and gardeners used predatory and parasitic wasps and flies, insect-eating birds, lizards and toads as agents of biological control. In the late 19th century sugar cane scientists carried cane toads from Barbados to Puerto Rico, to Hawai'i and then Queensland to control pests. Toads were introduced to some 138 countries, and are now ranked among the world's most invasive species. Queensland's sugar scientists...