Along with being producers of honey, commercial bee colonies are important to agriculture as pollinators, along with some birds, bats and other insects. A recent report by the National Research Council noted that in order to bear fruit, three-quarters of all flowering plants - including most food crops and some that provide fiber, drugs and fuel - rely on pollinators for fertilization. "I would characterize it as serious," said Daniel Weaver, president of the American Beekeeping Federation. "Whether it threatens the apiculture industry in the United States or not, that's up in the air." Scientists at Penn State, the University of Montana and the U.S. Department of Agriculture are among the quickly growing group of researchers and industry officials trying to solve the mystery.

Among the clues being assembled by researchers: - Although the bodies of dead bees often are littered around a hive, sometimes carried out of the hive by worker bees, no bee remains are typically found around colonies struck by the mystery ailment. Scientists assume these bees have flown away from the hive before dying.- From the outside, a stricken colony may appear normal, with bees leaving and entering. But when beekeepers look inside the hive box, they find few mature bees taking care of the younger, developing bees.- Normally, a weakened bee colony would be immediately overrun by bees from other colonies or by pests going after the hive's honey. That's not the case with the stricken colonies, which might not be touched for at least two weeks, said Diana Cox-Foster, a Penn State entomology professor investigating the problem.