Book T of C
Chap T of C
So-called "lower" organisms often show sophisticated learning abilities, when this aids their survival and reproduction. Bees and their relatives are especially good at learning the location and appearance of flowers.
What is the waggle dance of the bee?
Bees communicate location information to their fellows with the famous waggle dance first described by Von Frisch (1974). A bee returning to its hive, if it has found flowers, makes a distinctive wiggle of the abdomen and dances up the side of the honeycomb. The bee's angle from the vertical indicates the angle of the flower away from the sun. A dance 100 degrees to the left of the 12 o'clock position indicates flowers can be found 100 degrees to the left of the sun, as seen from the hive.
If the food is found by flying away from the sun, the bee dances downward rather than upward. The duration of the dance tells other bees the distance of the pollen source (a fast dance indicates food close by). Von Frisch also identified other factors that aid bee navigation, such as odor particles borne by the foraging bee that returns to the hive.
Von Frisch won a Nobel Prize for his work, but many scientists challenged it in various ways. Some suggested that bees responded to sounds rather than the dance, although other researchers believed bees were deaf. Some suggested that bees used odor alone to direct their hive mates, and the waggle dance was irrelevant.
These controversies were seemingly put to rest by detailed research carried out by the team of Wolfgang H. Kirchner, of the University of Wurzburg in Germany, and William F. Towne, of the Kutztown University in Pennsylvania. They devised robot bees that delivered messages using waggle dances, or by delivering samples of pollen, or by producing a vibrating sound similar to the beating of wings. Among other things, Kirchner and Towne discovered the following:
How did researchers test the "waggle dance" theory with robot bees? What other discoveries did they make?
—Bees can indeed hear, "and their ears are well suited for detecting the sounds associated with the dances."
—"Both sound and dance are needed to communicate information about the location and the food." A bee with clipped wings, which raised the frequency of the sound produced by the dancer, could not recruit other bees.
—Bees in the audience of the hive may rub their thoraxes against the comb, producing a squeak that vibrates the comb. This causes the dancing bee to stop the dance and dole out samples of food, "so that her audience knows not only the direction and distance to the feeding site but how the food smells and tastes as well."
—A robot bee, dabbed with a faint floral fragrance and "waggled" by a step motor, successfully guides bees to a sugar solution placed in a distant field. (Kirchner & Towne, 1994)
What is evidence that bees form cognitive maps?
Gould (1986) showed that bees form detailed cognitive "maps." They optimize their routes to flower locations, taking the shortest route when visiting multiple sites. Bees refuse to respond to a waggle dance that points to the middle of a lake. However, they respond to a waggle dance that points to the opposite shore of a lake.
Does it sound unrealistic to suggest that "pictures" and "maps" could be preserved in the tiny heads of insects? The bee brain is tiny compared to a human brain, but it is nevertheless a complex system with over 200,000 different nerve cells. No wonder they can carry out some complex information processing.
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Copyright © 2007 Russ Dewey