Michael Gross looks at widespread reports of the disappearance of honey bee colonies.

Bees have many natural enemies. It's not just bears that take a shine to the honey and/or the immature insects. There are also yeasts and parasitic insects that threaten to rob the colonies of the rewards of their hard labour. Researchers recently found that one parasite, the small hive beetle, even uses the bee's alarm pheromone as a signpost to congregate on stressed hives.

With this and the inevitable problems of the cold season, beekeepers are used to observing some losses after each winter. This spring, however, many bee keepers across North America have reported many losses, often with no discernable cause. If parasitic mites had conquered the hives, they would leave tell-tale signs, as is known from previous die-offs. In contrast, what appears to have happened this time, is that hives remained empty for the simple reason that bees flew out and never returned.

By April, similar observations have been reported from 27 US states. In some areas, even experienced beekeepers saw three quarters (or more) of their colonies disappear. Scientists were baffled by the phenomenon and coined the phrase Colony Collapse Disorder (CCD) to refer to it.