Bees are in need of their own Sherlock Holmes. Since 2006, beekeepers have been reporting the disappearance of most or all adult bees in hives, a phenomenon called Bee Colony Collapse Disorder. The queen bee and young bees are still there. There are no dead bee bodies and no adult bees at all. Perhaps they need Fox Mulder instead. It's like the bees were abducted.
No one is quite sure this is happening. Bee colonies sometimes lose a lot of bees over the winter, but not like this.
There are a few possible culprits and no single one seems to be the sole issue. Mites and internal fungi are common in colonies that collapse, but are also found in healthy colonies. One theory is that the problem is when the total number of these reaches a certain level.
Bees are also affected by stress. Yes, it even afflicts insects. Nectar and pollen availability and quality are a problem. Managed bees are also affected by beekeepers moving the hive around or the hive getting too crowded. Makes us crazy, too.
Pesticides may be an issue, though no one pesticide alone seems to be the culprit. It could be an issue of how pesticides are used or a combination of pesticides.
The going theory is that it is a few of these factors together that are behind the collapse. Scientists are still hard at work figuring this out.
There are lots of theories, but one big problem for humans. Many plants, including important agricultural crops, depend on bees for reproduction. Per the USDA, "about one mouthful in three of our diet directly or indirectly benefits from honey bee pollination." Yikes.
How are bees and our crops connected? Honeybees coevolved with flowering plants. This means that the bees evolved over time to use the resources provided by flowering plants, while the plants were evolving over time to depend upon bees. Bees pick up pollen and nectar provided by flowers. They use nectar to make honey and eat some of the pollen as food. Some of the pollen, however, is spread between flowers as the bees forage. This pollinates the flowers, creating a whole new batch of flowers, which means for us a whole new batch of fruits and vegetables. The bees and flowers need each other and we need them.