IN 2006, beekeepers in Pennsylvania’s apple country noticed the first sign of many bad things to come. Once thriving beehives were suddenly empty, devoid of nearly all worker bees, but with an apparently healthy, if lonely, queen remaining in place. Over a period of just three months, tens of thousands of honeybees were totally gone. Multiply this across millions of beehives in millions of apiaries in the more than 22 states that were soon affected, and suddenly we faced a huge, tragic mystery. Up to 24 percent of American apiaries were experiencing colony collapse disorder (C.C.D.).