All bumblebees always aren't as busy as, well, a bee. It all depends on what their job is.
Researchers have known that a key to the insects' success in adapting to cooler climates is their ability to maintain fairly stable body temperatures when flying to flowers. Whether and how they maintained nest temperature was poorly understood. But now scientists from the University of Washington and the University of Puget Sound have peered into bumblebee colonies and have discovered some answers.
By exposing bumblebee nests to a range of temperatures, the researchers found that the workers are effective at buffering the nest from temperature extremes. Some workers specialized in raising the temperature in a nest when they incubated the colony's young developing bees or brood. Other workers fanned their wings to cool the nest when the temperature became too hot.
Performance of various in-nest tasks is not interchangeable among these social insects. Instead, the researchers found strong evidence for job specialization, even when a colony was artificially forced to step up its rate of incubation, according to Sean O'Donnell, a UW associate professor of psychology and member of the research team.
The researchers challenged colonies by removing their most active incubating workers and lowering the nest temperature. One group of bees was consistently involved incubating across a range of temperatures. In a second experiment, the researchers removed the most active incubating workers. When this happened a colony's remaining incubators responded within 24 hours by increasing their rate of incubation, rather than having workers involved in other jobs switch tasks, said O'Donnell.
Bumblebee workers vary considerably in size, and body size affects which tasks individuals perform.
"We expected that larger workers would be incubators, but we found to our surprise the opposite was true," O'Donnell said. "We don't know whether the smaller
Contact: Joel Schwarz
University of Washington