Although selenium in very low concentrations is necessary for the normal development of insects -- and humans -- it becomes toxic at only slightly higher concentrations, researchers at the University of California, Riverside, said.
In many Pacific Rim countries and near coal-fired power plants worldwide, selenium occurs most often in soluble forms, such as selenite, which can be taken up by plants that then incorporate the element into their nectar and pollen that the bees gather, the researchers said.
Bees feeding on these food sources can inadvertently take in significant amounts of selenium, researchers said.
"Nature has not equipped bees to avoid selenium," entomology Professor John T. Trumble said in a university release. "Unless the rates of concentrations of selenium were extremely high in our experiments, the bees did not appear to respond to its presence."
Bees that had been fed selenate in the lab were less responsive to sugar (as sucrose), which interfered with their foraging behavior.
"The selenium interfered with their sucrose response," researcher Kristen R. Hladun said. "Such bees would be less likely to recruit bees to forage because they wouldn't be stimulated to communicate information about sucrose availability to the sister bees."
Also, forager bees that were fed selenium in moderate amounts over a few days in the lab died at a significantly younger age, the researchers said.