Waggle Dance Essay, Research Paper
Communication Among Honeybees
In every bee hive there are three types of bees, a queen, drones, and many workers. The lone queen honeybee is a fertile female, while the drone honeybees are males that are exclusively used for reproduction. It is the many worker honeybees, infertile females, that are responsible for foraging for food.
For hundreds of years biologists and naturalists have noticed that the worker honeybees do not all go out to search for food at the same time, but rather send out scouts ahead. These scout honeybees locate the food, return to the hive, and then the rest of the workers go to collect the rest of the food. Many scientists, dating back to Aristotle, have been baffled by how the worker bees are able to locate the food sought out by the scouts. How do the scout and worker honeybees communicate in the hive to alert each other where to forage for the food?
In 1943, an Austrian entomologist, Karl von Frisch hypothesized that the scouts were able to communicate the necessary information to the other worker bees by moving in specific patterns after returning to the hive. He called this movement the waggle dance . Karl von Frisch said that the waggle dance of the honeybee was able to communicate the distance, the direction, and even the type and amount of food to the other worker honeybees. He published his findings in a book called The Dance Language and Orientation of Bees, and later received the noble prize in 1973 for his breakthroughs in animal behavior.
Before he published his findings, Karl von Frisch spent years experimenting and recording observations to try and solve the mystery of honeybee communication. He started by placing a dish filled with sugar water a short distance from a bee hive. He noticed that immediately after placing the dish outside, the dish was swarmed with many honeybees. As the dish continued to empty, increasingly less honeybees came to it. However, if he refilled the dish and one of the bees came to it, then a short while later the dish was once again swarmed with bees. He concluded from this that the scout bees must communicate the information regarding the food to the worker bees when returning to the hive. In order to try and understand how the bees communicated, Karl von Frisch and his colleagues built a transparent bee hive. They marked the scout bees with red dye on the thorax, and observed that when the scout bees returned to the hive it began to do a series of dances that where immediately followed by many worker honeybees swarming to the food source. Karl von Frisch concluded from this that this dance which he observed was the form of communication between the honeybees.
After much analysis and experimentation, Karl von Frisch was able to dissect and begin to understand the different components and purposes of the honeybee s dance. He observed that there were two different dances; a round dance, and a waggle dance.
He found that the round dance was used if the food was within 50 meters of the hive. The round dance consists of the scout honeybee moving in small circles and reversing direction every few revolutions . After completing the dance, the worker honeybees that observed the dance leave the hive to forage for the designated food. From numerous trials, Karl von Frisch showed that the round dance does not convey direction or specific distance, but rather is used to quickly alert the hive that there is food close by.
The waggle dance is more complex, and is used when the food is located over 50 meters from the hive. The waggle dance is made up of two distinct parts, a straight run, and round turns . First the scout dances in a straight line while waggling its body very vigorously. Then the scout honeybee turns in one direction and makes a circular turn back to the start position. The straight run is then repeated, but this time the scout makes the circular turn in the opposite direction. After repeating the dance numerous times, the scout then stops and gives some of the other workers a taste of the food it has found. The worker honeybees that have just witnessed the dance are then able to go collect the specified food.
The different aspects of the waggle dance also convey different information. The direction of the straight part of the dance conveys the direction in which the food is located. The speed at which the dance is repeated conveys the distance to the food source.
Frisch noticed that when the hive was horizontal, the straight part of the dance was pointed in almost the exact direction of the food source. However, it took many years of research to come up with an explanation as to how the honeybees are able to convert the direction of the straight run danced in a vertical hive, to the horizontal ground outside. Frisch noticed that if he kept the food source in the same location, the bees in the vertical hive would change the direction of the straight run proportionally as the day progressed. He was therefore able to show that the scout honeybee based the direction of the straight portion of the dance relative to the position of the sun in the sky. If the food was located in the direction of the sun, then the scout would dance the straight part straight up. If the food was at another angle in relation to the sun, then the scout would dance the straight part at the same angle to the vertical . The other worker bees will translate this angle when they leave the hive in relation to the angle between the sun and the food source by means of heat sensing as well as an internal clock that allows them to know where the sun is in the sky. The internal clock within the honeybees appears to be related to the honeybees metabolic rate.
The speed at which the scout honeybee performs both parts of the waggle dance is also very important. Frisch noticed, that the speed in which the waggle dance was performed indicated the approximate distance to the food source; the faster the dance, the closer the food. It was relatively easy for Frisch to understand the importance of the speed of the dance, as there is a lot of variation between the speeds of the straight part of the dance when using two different distances to the food source. Also, the faster the scout honeybee actually vibrates its body, indicates the quality of the food source. If the food source is extremely concentrated, then the scout will waggle with a lot of vigor.
Karl von Frisch s theory of honeybee communication went unchallenged and unchanged until 1960, when Adrian M. Wenner and Harald E. Esch began to question Frisch s hypothesis. Although they were both working in two separate places, Wenner at the University of California and Esch at the University of Notre Dame, they both questioned how, according to Frisch s theory, the honeybees were able to see the dance inside of the darkened hive.
Wenner suggested that the other worker bees were able to recognize the specific dance of the scout bee, not by seeing the dance, but by hearing and sensing the dance. He said, that when the scout performed the dance it caused vibrations through the hive which conveyed the dance s information to the surrounding worker bees. As well, Wenner observed that the bees also emitted very low frequency buzzing. He theorized that although the waggle dance is used to convey information regarding food between honeybees, it is only understood and communicated through vibrations.
Another problem that bothered Esch, was how the bees were able to judge distances between the hive and the food source. Esch realized that bees have compound eyes, and that they were able to judge distances by the flickering motions reflected into their eyes as they flew. This concept is know as the flicker effect . He proved this theory by doing numerous experiments, which involved setting up a food source in the middle of a tunnel, and then switching the tunnel when the other worker bees came to collect the food. When he did not change the tunnel, then the other workers were able to locate the food source immediately. When he replaced the original tunnel with a narrower tunnel with vertical stripes, which would cause more flickering, he found that the other workers would search for the food well short of were it actually was. Consequently, when the tunnel was replaced by a wider tunnel with stripes, which would appear to cause less flickering motion, he found that the bees started searching for the food farther past were the food actually was located. Esch, along with another scientist named Burns also discovered from the tunnel experiments, that the flicker motion in judging distances also effects whether the scout bee will dance the round dance or the waggle dance. They noticed that depending on the scenery, and the amount of flickering, the bees could be tricked into dancing the wrong dance. These findings fit in well with Frisch s hypothesis regarding the different dances being dependent on the distance.
About fifteen years ago at the University of Wurzburg in Germany, Professors Michelsen and Kirchner began to try and prove whether the honeybees communicated through the actual dancing, or whether through the vibrations and noises that the dance caused. For their experiments they constructed robotic bees that were capable of imitating the waggle dance, as well as emitting the specific noises and vibrations. After observing the effects of the robotic bees on numerous bee hives for five years, they observed, that if the robotic bee would just do the waggle dance without causing the vibrations, then the other worker bees would not leave to forage for the food. If the robotic bee only caused the vibrations and did not perform the waggle dance, then the worker bees would not forage for the food. However, if the robotic bee would perform the waggle dance as well as cause the vibrations, then the rest of the surrounding worker bees would leave and forage for the food. From these experiments, Michelsen and Kirchner concluded that the scout honeybees communicate with the other worker bees through a combination of actual dancing as well as through vibrations. Further experiments were done using the robotic bees in conjunction with Karl von Frisch s experimental data , allowing scientists to accurately control which food source the worker bees would forage at.
Although Karl von Frisch s theories on honeybee communication are widely accepted among the scientific community, there are many respected biologists and entomologists who do not agree with Frisch s theories. Many argue that although it appears that there is a direct connection between the scout bees dance and the recruitment of other worker bees to forage for food, there is not enough conclusive evidence that the dances contain as much information as Frisch ,and his successors, give credit for. It can be said, that the dances are just used in order to get the other worker bees attention, and the only communication is when the scout bee actually gives the other worker bees a sample of the nectar. After receiving the nectar, the other worker bees leave the hive, and are able to locate the food source by following floral aromas.
There are also many scientists who agree that honeybees do communicate through dance, but do not agree with Frisch s theory of the waggle dance. They believe that the honeybees communicate through different dances such as the DVAV dance and other vibration and spasmodic dances. Although it does appear that the honeybees may do these other dances as a form of communication, there is not enough experimental evidence to prove the significance of these other dances.
In 1996, while conducting experiments with honeybees, a scientist named Tautz discovered that the location in the hive in which the waggle dance takes place directly relates to the number of other worker bees recruited to forage for the food. In a bee hive there are two types of honeycomb, open empty honeycomb cells and full capped honeycomb cell. Tautz noticed that if the scout bee performed the waggle dance on an empty cell, three times as many worker bees would leave the hive to forage food in comparison to the dance being performed on a capped cell. He theorized that this occurred because the empty cell transmitted the vibrations of the waggle dance better then the capped cells. This theory helped prove Michelsen and Kirchner s experimental evidence that vibrations are an important part to honeybee communication.
There are many different theories as to how worker honeybees communicate. The most respected and proven theory being Karl von Frisch s waggle dance. Frisch s theory, along with later experimental evidence by Wenner, Esch, Burns, Michelsen, Kirchner, and Tautz, shows that the scout honeybees communicate and recruit other worker honeybees to forage for food through specific dances. The dances contain information on the direction, distance, and type of food, and are conveyed through both the actual dancing as well as through vibrations. Many factors, such as outside scenery and the location in the hive where the dance is performed, effect the accuracy and success in conveying the necessary information to the other worker bees. Although not all scientists agree with this theory, it is the only conclusive attempt to understand honeybee communication that has been proven through many different experiments by many different scientists, and is therefore the most accepted theory on honeybee communication used today. This theory, however, is not complete, and there are still many factors to communication between honeybees that are still unknown. In the future, by means of many more experiments and hypothesize, we will truly be able to understand the mysteries of honeybee communication.