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Bee death

Bee keeper Paul Lehmann displays a dead bee on May 19, 2008 in Mahlberg near Freiburg, Germany. According to the German bee keepers association in the last few days honey bees died massively due to the use of pesticides. Seed corn that was sowed in the last weeks is mostly treated with clothianidin, a chemical used to protect roots from pest. (Photo by Ralph Orlowski/Getty Images)

Bee death mystery continues

A common class of pesticide is causing problems for honeybees and bumblebees, important species already in trouble, two studies suggest. But the findings don't explain all the reasons behind a long-running bee decline, and other experts found one of the studies less than convincing.