This stings. A new study says that when Asian honeybees were introduced to Europe in the mid-20th century they carried a deadly wing-deforming disease known as DWV. While the imported insects had developed a resistance to the mite-borne virus, native honeybees were vulnerable. Later, the affected European honeybees were introduced to populations in America and other parts of Asia, leading to massive colony collapses. The virus is now spreading to other pollinators, and scientists warn that farmers should screen colonies to stem this major threat to agriculture.