The researchers studied Bombus huntii, a species of bumblebee common in the Pacific Northwest. Bumblebees, unlike most insects, are warm-blooded. They can heat their bodies, and can remain active at cooler temperatures than many other insects. To achieve optimum conditions for their young, bumblebees rely on nest thermoregulation, actively raising or lowering temperature. Because they are well adapted to cooler and temperate climates, bumblebees are important pollinators of a number of food crops including blueberries, cranberries, huckleberries and greenhouse-grown tomatoes, peppers and eggplants.
To study task performance, the researchers glued a numbered plastic tag to the thorax of workers in three colonies. They observed and videotaped the incubation and wing fanning, or cooling, performed by individual workers under four temperature conditions ?cold, moderate, warm and hot. Temperatures ranged from 10.3 to 38.6 degrees Celsius (about 50 to 101 degrees Fahrenheit).
The study focused more on incubation than fanning because the researchers did not want to raise the temperature too high. Excessive heat can kill bumblebees. In looking at the incubation behavior, O'Donnell said workers vibrate wing muscles to shunt down heat to their abdomen, which is held in close contact with a comb containing the brood.
"You can see them shiver to transfer the heat," he said.
"Task switching was previously thought to be common among bumblebee workers," said O'Donnell. "But this study indicates that there is strong specialization in labor among individuals, and body size seems to play a role in what jobs they perform. I
Source:University of Washington