Bees communicate by dancing
By PAUL G. JANTZEN
Contributing writer
Communication among animals of a group has long intrigued humankind. How do crows rally others of their flock to mob an owl? How do geese maintain their flight configuration as they migrate? How do bees inform others in the hive about the location and kind of nectar-bearing flowers?
How honeybees communicate with fellow workers was investigated by German zoologist Karl von Frisch and reported in the 1940s. He found that bees detect odors with their antennae. The odors they detect appear to be very similar to those we experience.
When a scout bee discovers a source of nectar or pollen in the neighborhood of the hive, she returns to the hive and performs a round dance on the vertical surface of the honeycomb. She follows a small circular path, once to the right, then to the left, always repeating in alternate directions. (Diagram 1)
She informs her fellow workers of the species of flower two ways. The antenna of the observing bee detects the scent of the flower on the body of the dancing bee. Then, during pauses in the dance, the dancer feeds the observing workers a droplet of nectar from her honey stomach. The odor of the nectar is unique to the plant species. The richer the source of nectar, the more vigorous is the dance, and the greater is the number of bees that leave to collect more nectar.
But bees may gather food several miles from the hive. It would be useful for a foraging bee to know the distance and direction of distant sources of food.
Again, von Frisch demonstrated with simple but painstaking experiments how honeybees communicate this information when the food sources are more than 100 meters from the hive. For this, the bees perform a tailwagging dance on the vertical surface of the honeycomb. They run a short distance in a straight line while wagging the abdomen rapidly. Then they turn to the left and circle around to repeat the original straight line, but this time circling round to the right, only to repeat the pattern again and gain, always following the path of a figure eight. (Diagram 2)
The distance of the food source from the hive is indicated by the number of turns in the wagging dance within a given time. At 100 meters, von Frisch observed nine to 10 complete cycles in 15 seconds; at 6000 meters (3.6 miles), only two cycles in 15 seconds.
The direction of the food from the hive is indicated by the direction of the tailwagging part of the dance. When the food source is in the horizontal direction toward the sun, the straight portion of the figure eight wagging dance is straight up on the honeycomb. If the food source is at some angle to the right or left of the sun, that portion of the dance is at the same angle to the right or left of the vertical line. When the sun is directly overheard, this sort of communication ceases.
If the dancing bee is kept in the hive for a while, she shifts the direction of her dance to compensate for the shifting of the sun's direction. She can detect a one- to two-degree difference in the sun's position. And that requires a built-in time sense.
When the sun is invisible, says von Frisch, honeybees orient their dance and therefore their flight according to the pattern of polarized light in the sky which depends on the sun's position. Kansas University entomologist Charles Michener says that, in light cloud cover, bees navigate according to the ultraviolet rays of the sun.
von Frisch's initial observations were made on Austrian bees. Other varieties of the same species, he discovered, have somewhat different patterns of communication — different dialects. The Austrian honeybee changes from a round dance to a wagging dance when the nectar source is found beyond 820 meters (275 ft) from the hive; Italian bees change at 36 meters (120 ft). So when a colony of bees is composed of both varieties, or of hybrids of the two varieties, some of the bees do not follow the directions correctly. Austrian bees dance somewhat faster for a given distance. So an Austrian bee instructed by the wagging dance of an Italian bee will search for nectar too far from the hive. Furthermore, in the switch from the round dance to the wagging dance, Italian bees have a twisted intermediate dance which only Italian bees understand. This is clear evidence of a genetic basis for this aspect of bee behavior.
Karl von Frisch also demonstrated that bees can distinguish yellow, blue-green, blue, and ultraviolet colors, but not red. So both odor and color of flowers attract the scout bees that transmit their discoveries to the colony. Color may also aid in finding nectar glands in the flowers bees visit. The entrance to the tube containing a flower's nectar is often a different color, or a different shade of color, than surrounding parts. Those color differences usually appear as contrasting in the eye of a bee. We could call them nectar guides.
Thirdly, when bees have found a population of nectar-rich species of plant, bees of a colony can continue to visit that species for days. As they become familiar with a type of flower, they save time not having to learn how to extract nectar from a variety of flowers.
How the foraging bees know where and from which flowers to get nectar, even if the dancing scout remains in the hive, is indeed remarkable. One might be tempted to attribute to honeybees a high degree of intelligence. But says, von Frisch, "The brain of a bee is the size of a grass seed and is not made for thinking. The actions of bees are mainly governed by instinct."
And yet, as he ponders the message provided by the wagging dance, he concludes that "the amount and precision of the information far exceeds that of any other known communication system among animals other than man."
