Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [99]
Many biologists were convinced that the bees do indeed use the information in the dance by some experiments published in 1975 by James L. Gould, in which he manipulated the dancer to "lie" about where the food was located using a flashlight to mimic the sun and, hence, alter the angle at which the dance was produced relative to the sun's actual position. Wenner was unconvinced, suggesting that the experiment was never replicated, and he and a few other scientists also claimed that Gould did not fully control for the bees' use of odors as an alternative explanation.
Several scientists have tried to manufacture artificial bees that could be made to dance inside the hive to further test the hypotheses, and one of these was able to recruit at least some bees to the food source it was programmed to dance about to the rest of the colony. Wenner once again dismissed these findings as inconclusive, and it is certainly the case that the mechanical bees didn't do the job nearly as well as a real one.
The conclusive set of experiments, at least in the majority of scientists' view, came from H. Esch and colleagues, who were able to manipulate something called the optic flow perceived by the bees. Bees measure distance by gauging the way images in the environment move across their eyes as they fly, rather like clocking the trees that tick by the windows of a moving train. The scientists trained the bees to fly through a tunnel lined with a black and white pattern that presented an optical illusion to the insects, making it appear that they had flown a longer distance than they actually had. When the fooled bees got back to the hive, they produced a dance that indicated the food was farther away than it was. The recruits promptly flew to the wrong site, indicating that they had indeed been misled by the dance itself.
Yet other studies used harmonic radar to track individual bees and the flight paths they took to the feeder or flower patch; these showed that most of the bees recruited by a dancer took a straight path to the food, rather than zigzagging back and forth the way they would be expected to if they were simply using the odors in the air to find the patch that smelled like the dancer inside the hive.
Finally, my friend Kirk Visscher and a former student of his, Gavin Sherman, demonstrated that the waggle dances help the bees survive in nature. In a clever experiment, they used lighting to mimic the sun and misdirect the bees, so that the dances didn't help the members of the hive to find a food source. They allowed a control set of colonies to dance appropriately. At the end of the season, the deceived colonies had accumulated significantly less honey than those in the control group, an important consideration in the well-being of the hive.
No one, including Kirk, disputes that the bees also use the odor information from the initial dancer to find food, and that under some circumstances the dances are not needed for the colony members to find out where they can forage. At some times of year, the bees can find plenty of nectar by relying simply on the flower odors in their environment that are carried on the bodies of the workers that find each patch of blossoms. But when the going gets tough, the bees seem to need dancing. Some theoretical work by Madeleine Beekman and Jie Bin Lew of the University of Sydney in Australia formalized this mathematically, demonstrating that dancing helps a colony concentrate on the best food sources in the area and not waste time sending workers to a low-quality patch. It is most helpful when the probability of finding a patch on one's own as an independent forager is relatively low, because the dance allows the colony to exploit only the richest nectar sources.
Bilingual Bees?
WHERE did the bee dance language come from? I suggested earlier that scientists believe it may have evolved from the need to