Specialized workers build queen cells with a distinct wax that appears to influence the larvae
A queen bee can be shaped by more than just her famous royal diet.
The wax of the peanut-shaped room where the queen develops has distinct physical and chemical properties that help guide its developmentreport the researchers on June 3 in Nature. By analyzing the composition of the chamber and the larvae it houses, the team challenges the long-held idea that royal jelly alone – the food used to make the queen and given to the selected larvae – makes a queen.
“The finding is very interesting and thought-provoking,” says Thomas Seeley, a biologist at Cornell University who was not involved in the work. “To me, queen cells have long seemed important, because the odors of a developing queen can permeate the wax walls, marking them as very special places that workers recognize and don’t accidentally damage.”
But for entomologist Boris Baer, the cells posed a question born from years of observing his own colonies. “Bees spend so much time and energy building these cells that it would make little evolutionary sense if they were just larger food containers,” says Baer, of the University of California, Riverside. “Could the cell itself contribute to the development of the queen?
Baer and his colleagues studied western bees (Apis mellifera) and oriental bees (Apis cerana), comparing the wax of queen and worker cells, the workers that build the cells, and how the larvae behave in each wax environment.
The first clues came from the wax. Analyzes showed that queen cell wax is softer, less dense and chemically distinct from worker cell wax.
The next discovery was a surprise, Baer says. “Royal nurses” building “royal nurseries” for their future queens “spend more time [than worker cell builders] building these cells, run hotter than other bees and have distinct patterns of genes [activity]”, which suggests that they are specially adapted to modify the wax they work with.
But the strongest evidence came when the team let queen-destined larvae grow on royal jelly for four days, then replaced the caps of their artificial queen cells with wax from queen or worker cells. Up to about two-thirds of the larvae under the worker cell wax died, compared to about one-third under the queen cell wax. They also developed into smaller pupae, while queens raised under the queen cell wax looked more like those left intact in their natural cells.
“Everything supported the same conclusion,” Baer says. Bees do more than feed the queen: they actively “make” her.
Exactly how this engineering works remains unclear. Kai Wang, an apiologist at the Chinese Academy of Agricultural Sciences in Beijing, says the distinct chemical smells he and the team found inside the cells are particularly intriguing. “Do they influence the queen’s developing senses, preparing her for mating and life after emergence?” he asks himself. “Are some produced by the larva itself? And could the future queen actively communicate with the workers building her room?”
The researchers plan to trace when the wax’s environment exerts its effects during development. But the implications go beyond the queen’s development, Baer says. “These superorganisms mobilize specialized workers who collectively shape the next generation,” he says. “The division of labor in bees could be much more complex than we have acknowledged so far.”