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The dance language of honeybees






 

The dance language of the honeybee is the most complex animal natural language that has been decoded, at least partly. Successful forager honeybees (Apis melifera) are able to recruit other bees to a distant food source (or water, or resin, or a new nest site) by specific dance movements together with other components such as odours and sounds. As Manning (1979) notes, after Karl von Frisch described signals in the bees hive as elements of complex language, the world should admit that information in a symbolic form is available not only to man, but to such a modern creature as the honeybee.

The suggestion that honey bees can inform their nestmates about the location of a rich nectar source when they arrive to the hive, was made by Aristotle and since repeated more than once. Aristotle himself documented a honeybee's ability to recruit her nestmates to a good food source but did not speculate on how the communication took place. He and other naturalists did, however, observe that a bee that finds a new food source returns to the nest and dances for her sisters, rather than feasting alone. Pliny reportedly constructed a hive that had a window made from transparent horn, through which he could monitor dancing bees. The hypothesis about transferring information among honey bees was given in scientific literature firstly by Spitzner in 1788. Famous explorers of social insects of nineteenth century such as Dujardin, Emory, and Lubbock also suggested that honey bees possess a kind of language that enables them to inform their nestmates about locations of the food. Nevertheless it was difficult to explain how insects can do that.

The dance language is an uncommon form of natural communication by which animals inform each other about remote objects. This form of communication is sometimes called distant homing and only single cases have been described in scientific literature. Among them chimpanzees in Menzels (1973 a,b) experiments which hypothetically passed each other the information about hidden objects, and ants that inform their nestmates about location of the food distantly lacking the possibilities to use smell trails and other ways of information transfer except contacts with a scouting individual (Reznikova, 1983, 2004). In terms of modern theory of social learning distant homing may be called social learning from information centre.

The honey bees should possess a powerful communication system in order to inform specimens about an exact location of the desired remote object. Von Frisch suggested that in the dance language, an abstract, or symbolic, code is used to transmit the information about the direction and distance of a desired object. In contrast to ants with their difficult -to- handle movements of antennae, forelegs and maxillas, honey bees demonstrate distinctive movements in the darkness of the hive. First von Frisch (1923) suggested that the bees have language but only as stimulus-response. Later he assigned smell of the food source as primary importance for transferring information among bees (Frisch, 1937). After series of special experiments with changing locations of artificial feeders accompanied by observations within a glass-walled hive, von Frisch came to a conclusion that the bees give others exact data about the source of food by means of dance language.



Von Frisch (1947, 1967) described three forms of dances. A simple round dance serves as recruiting signal for rich food sources close to the hive (50 100 m). Being activated by the round dance, bees leave the hive and search for nectar in the vicinity of the hive. At greater distances (100-150 m) a stickle dance is performed. The waggle dance informs the bees about distant sites, that could be located up to 12 km but more often are located not far than 3-5 km. The waggle dance is named from the waggling run in which the dancer wags her body from side to side and emits sounds by vibrating her wings. In the waggle dance, the dance path takes on a figure-of-eight shape: the dancer runs in a straight line (the waging run) and circles back, alternating between the left and the right return path. The direction of the wagging run relative to the vertical (gravity) on the comb indicates the direction to the food relative to the suns azimuth in the field. If the scouting dancer waggled while facing straight upward, toward the 12 on a clock-face, then the food could be found in the direction of the sun; if she waggled 60 degrees to the left of 12, facing the 10 on a clock-face, then the food lay 60 degrees to the left of the sun. In addition, von Frisch noticed that how fast the dancer completed her circuits corresponded to the distance between the hive and the feeding site: the closer the food, the more frenzied her pace. A few follower bees keep close contact with the dancer, and these bees may be recruited to visit the food. Von Frisch and his colleagues made detailed accounts of the dance language. With a stopwatch close at hand, they could observe the dance, decipher its meaning and then locate the food supply of which it spoke.



Years after von Frisch interpreted the symbolism of the dances, other components of the bees communication system have been appreciated. Esch (1961) and Wenner (1962) found that dancing bees make sounds during their waggling run. Later it has been revealed that the sounds the foragers produced could vibrate the combs under their feet as they danced (Eskov, 1979; Tautz, 1996; Tautz et al., 2001). The comb vibrations might then advertise the dance to those bees who could not otherwise see the forager. Levchenko (1976) revealed effective combinations of tactile, acoustic, and odour components of the communication system in honey bees.

Suggesting, as von Frisch did, that bees have a symbolic language aroused the scepticism of some other scientists, who continue to this day to favour von Frischs earlier idea that scent alone guides bees. Gould (1974, 1975) punctured the odour hypothesis. He showed that a forager can dispatch her nestmates to a site she has never visited. Such a feat would be impossible if the recruits relied on odours alone to track down a feeding site. The event could occur, however, if the searching bees gave priority to the information they received from the dance. In these experiments, Gould placed a bright light in the hive, which the dance followers mistook for the sun. In doing so, they interpreted the dances erroneously. These misdirected bees most often searched in the field using the misaligned dance information and seemed to ignore other cues such as odour. Gould concluded that they evidently preferred the message given in the dance to the other signals. Finally, the experiments using an artificial model of a bee confirmed von Frisch's hypothesis; the dances do indeed represent a sophisticated form of communication (see:Kirchner and Towne, 1994).

It is a natural idea to communicate with the bees through the mediation of an artificial bee. Indeed, a crucial test for any communication system is to experimentally modify it. The idea of using a mocking bee that dances and indicates the distance and direction of a target the other bees had never visited, was suggested a long time ago. In one of his pioneering papers devoted to the successful use of a robotic bee Michelsen (1993) cites The Future of Biology by J.B.S. Haldane (1927): We may be able to tell our bees to fertilize those apple trees five minutes fly to the south-east. To do this we should presumably need a model bee to make the right movements, and perhaps the right noise and smell. Since 1957 several attempts have been made to recruit bees by means of mechanical models of dancing bees (Steche, 1957; Esch, 1964; Gould, 1976; Lopatina. 1971; Levchenko, 1976).

Michelsen and colleagues (Michelsen, 1993, 1999; Michelsen et al., 1990) built a bee of brass and beeswax with a piece of a razor blade to represent the wings. Their robot bee could buzz its wings at the requisite 280 cycles per second (Hz), waggle its bottom and dance in a circle. It could also deliver drops of sugar water to the dance watchers. Using a computer to control the robot, the researchers set their robotic bee to dancing, attempting to dissect the components of the dance. Dancing a normal waggle dance, this bee, like any robot, was a bit clumsy (Fig. IX-3). Nevertheless, recruits in the hive used the information to fly to a target. On another day, researchers sent the bees in the opposite direction. Bees found new targets regardless of the wind direction, correctly following messages from the robot-bee that never left the hive itself. These studies allow us to reject the hypothesis that bees use smell of the new food source as the main source of information in favour of the hypothesis of the use of dance parameters to decide where to fly.

The honey bees dance language is considered symbolic in many respects. For instance, the exact relation between the velocity of the waggling run and the distance to the desired site is determined by local agreements, or dialects. For the bees studied by von Frisch, each waggle of the dance indicated that the desired site was located an extra 45 meters from the hive, for bees in Italy this figure is 20 meters, and for Egyptian bees it is 12 meters (Boch, 1956). It is important that all bees in the hive follow the same rule. The dance language meets the arbitrary criterion. For instance, the bees can in some cases use the direction to the desired site relative to the north azimuth instead of the suns azimuth (Gould and Gould, 1988). The dance language exhibits the displacement feature because the dancers can inform other bees about evidences distant both in space and time. The scouting bee keeps the suns trajectory in mind during several hours and corrects her dance in accordance with the daily movement of the sun.

It is still an open question to what extent can bees display creativity and flexibility of communication. It is known that the bees can communicate within specific limits. At the same time they speak not only about flowers. For example, it has been noted that quartermasters use figures of dances in order to indicate the location of a new nest site. They dance directly on a surface of a swarm of bees intended to relocate to a new place (Lindauer, 1961). It has been revealed recently that signals for house hunting are performed by a small proportion of the older (and possibly more experienced) bees. They perform waggle dances accompanied by the vibration signals (Lewis and Schneider, 2000).

Honey bees are not only capable of changing topics of their communication but also of producing and interpreting signals under circumstances not previously encountered. Lindauer, being then a PhD student and then an assistant of von Frisch, recalled their join experiment in 1948 when they moved an observation hive from its normal vertical position to a horizontal position and were surprised to see that bees dancing on a horizontal comb could indicate a direction to a food source (see: Seeley et al., 2002).

The role of cultural transmission and social learning is weak in the functioning of honeybees dance language. Lopatina (1971) demonstrated that young bees have to complete their innate stereotypes with the gained experience in order to receive messages from dancers. There are, however, many experimental evidences that details of the way in which the dance is performed and interpreted is determined genetically (Gould and Gould, 1988; Seeley, 1995). For instance, dialects in the dance language of bees from different races do not reflect any influence of social learning. If the pupae of one race are placed into the colony of another, then when the bees hatch, they persistently behave in a manner that is appropriate to their real sisters and they are not influenced at all by their foster sisters. Studies of the last decades (Rinderer and Beaman, 1995; Johnson et al., 2002) have shown that each of the transition points in honey bees dances (round-stickle, stickle-waggle) is controlled by a single gene showing simple Mendelian inheritance. Researchers are in agreement now that the dance is a complex honeybees behaviour under simple genetic control. However, it is possible that honey bees are capable of flexible transposition of inherited elements of their communication in conformity with changeable environment and new challengeable tasks.



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