for National Geographic News
Bumblebees prefer their food warm and learn to locate hotter flowers using color as a cue, scientists say.
The findings may have broad implications for the evolution of flowering plants.
To attract insect pollinators, flowers offer a nutritious reward of nectar and pollen. Now biologists say many flowers may encourage visits by offering a "heat reward" as well.
By consuming warmer nectar, bees may save energy they would otherwise have to spend maintaining their own body temperature.
"Bees can raise their body temperature to above 37 degrees Celsius [98.6 degrees Fahrenheit], even if it is just a few degrees above zero outside," said Lars Chittka of Queen Mary College, University of London.
"But this is costly, so collecting warm nectar is a clever idea."
Many flowering plants have features that allow them to increase the temperature of their flowers.
The scientists suggest that providing hot meals might be a shrewd evolutionary adaptation for plants, whose own reproduction depends on attracting pollinators.
The research will appear in tomorrow's issue of the journal Nature.
(Related story: "Buzz Kill: Wild Bees and Flowers Disappearing, Study Says" [July 21, 2006].)
Previous work has shown that some insects are attracted to warmer plants. In tropical rain forests, for example, scarab beetles spend much of their time deep inside flowers capable of generating heat through chemical reactions.
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