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Waterbury prof's research sheds light
on career specialties - in honey bees
It's a dirty job and only about 1 percent do it at any one time. But middle-aged honey bees that serve as undertakers - removing dead bees from the hive - appear to be a distinct cadre of workers that are developmentally ahead of their peers.
In the social world of honey bees, known for its division of labor, researchers have made unexpected discoveries: undertakers don't get better with experience and they don't do well working together.
The findings are detailed in two papers by Stephen T. Trumbo, an assistant professor at the Waterbury campus, and University of Illinois entomologists, Gene E. Robinson and Zhi-Yong Huang. The study of development appeared in the September issue of Behavioral Ecology and Sociobiology. The research on the undertakers' learning, or lack of it, was published in the fall issue of the journal Ethology.
"Understanding the career choices of bees is a useful model for understanding behavior in general," Robinson says. "This new information should enable us to develop new hypotheses about how neurons and genes in the brain function to produce the marvelously complex behavior seen in honey bee society."
The work - which involved identifying the undertakers, marking them with tiny, colored and numbered plastic tags, and following them closely through middle age - provides the first close look at undertakers. Since bees' nests are built in cavities, such a specialty is important for keeping the nests from filling up with the bodies of dead nestmates.
"Undertakers have very similar activity levels as other bees," Trumbo says. "They just do a little bit less of the other middle-aged tasks, like building the comb and storing food brought in by older foragers. They also remove debris, which fits in nicely with undertaking."
Undertakers also develop slightly faster than other middle-aged bees, moving on to foraging before food storers and hive builders. Middle age lasts about 10 days. Undertakers usually remove dead bees for a day or two, but "one extraordinary bee remained at the task for 13 days," Trumbo says.
Undertakers respond to the odor of the dead, locating bodies and carrying them out of the hive for 50 to 100 meters before dropping them. The researchers also monitored how swiftly undertakers worked.
"We didn't find any evidence for learning for this particular task," Trumbo says. "This rules out one of the major hypotheses that has been put forward for the advantage of middle-aged specialization: that specialists within social insect colonies will get better and better at what they do."
Previous research had shown that learning is important for the older foragers, who get more efficient as they learn what flowers are producing nectar at what time. The undertakers, however, do not improve in efficiency, Trumbo says. They also get in each other's way when two attempt to remove the same dead bee, thus slowing them both down.
Robinson had shown previously that some bees are genetically inclined to be undertakers. "We're beginning to get a clearer picture of the behavioral profiles of interesting types of specialist bee, such as undertakers," he says.