Barry Donovan:
Several papers published during the last few years on communication in
other species of social bees in the genus Melipona have shown that they
have an ability to pass on information about food sources using a
`language'. There are several hundred species in the Meliponinae, of
which only a few have been studied so far. It will be most interesting
to see if evidence of `language' is found for any other species.
Julian O'Dea: Here is an unpublished paper that touches on this matter:
Problems with the Honeybee Dance Language Hypothesis
Julian O'Dea, Visiting Fellow, Division of Botany and Zoology, Australian National University.
The "dance" of the honeybee (Apis mellifera L.) is one of the most famous of all animal behaviours, but its meaning remains controversial. On returning to the hive after a successful foraging trip, a honeybee may do a "dance," a set of movements that reflects in miniature the details of her trip. The duration and orientation of the movements in the dance depend on the distance from, and the direction of, the bee's latest foraging site relative to the hive. A longstanding debate centres on whether this "dance" is a language, in the sense that it communicates this spatial information to other bees, as famously proposed by Professor von Frisch. An alternative hypothesis is that locality odour alone, not dance movements, is the basis of the communication of the whereabouts of resources (1).
An assumption of the classical von Frisch hypothesis has been that honeybees are good at accurately estimating the distance they have travelled, so that they can represent this in their dances for the information of other bees. It has generally been thought that honeybees rely on the amount of energy used on a trip to estimate the distance travelled (2, 3).
However "dance language" proponents recently obtained some unexpected experimental results (4). They found that the relationship between the distance to resources and dance duration (which is supposed to reflect the distance the bee has travelled) differed depending on the direction to the food. This suggested that the honeybees were not able to make absolute measurements of distance travelled. Esch et al. (4) concluded that bees actually measure distance from the amount of "optic flow" on their trip, that is "the total amount of image motion en route to the food source". Since the amount of optic flow differs depending on the visual features in the honeybee's journey, this would explain why the bee's estimation of distance might vary depending on the direction of her flight. But, at the same time, it implies that honeybees must be poor at measuring distance in an absolute sense.
If Esch et al. (4) are correct, their findings raise problems for the "dance language" hypothesis. As they note themselves, the apparent lack of absolute accuracy in the information about distance - supposedly conveyed in the dance - is a problem for the proposed communicative mechanism. In the absence of accurate distance information, as the authors write, " ... there must be a high selection pressure to ensure that a dance signals the direction of the food source as precisely as possible." However there is evidence that direction information is also not very accurate (5).
The inaccuracy in the supposed means of communication makes it less likely that the dance movements of honeybees have anything to do with communication of the whereabouts of resources. The alternative, locality odour hypothesis (1, 6) therefore gains in credibility.
Further evidence that bee species may show behaviours on returning from a foraging trip that contain information about the trip that is not communicated to the other bees in the hive comes from observations on stingless bees (Meliponini) (6). A study on Melipona quadrifasciata (7) found that there was a correlation between the distance to resources and the duration of the sounds emitted by foraging bees on their return. However, the study also showed that the distance information is probably not used by the other bees in their foraging. For example, although the bees were found to respond to a sound signal that corresponded to a nearby feeding station (0 to 30 m), "the bees did not respond to a signal for a feeding station 300 m away or for a station at any other distance". The authors concluded that " ... smell [locality odour] alone appeared to be a sufficient stimulus for the trained bees to fly to the 300 m feeding station."
More recent studies (8-10) on another Melipona species, Melipona panamica, also indicate that the bees make sounds on returning to the hive with features that correlate with details of their foraging trips. The authors propose that these sounds communicate the position of food localities to other bees. However, little consideration was given to the possible communication of the odour of food localities in providing information on their whereabouts. No experiments were done that would have determined whether the locality odour bees bring back from a desirable foraging site, or the sounds emitted by bees on returning from the site, is the factor that conveys information on the location of resources. It is quite conceivable that - as in the case of Melipona quadrifasciata (7) - the sounds produced by the bees that correlate with details of their foraging flights are not the mode of communication.
In summary, it is conceivable that food locality odour is used by bees in communicating the whereabouts of resources, not the supposed "dance language" and other postulated forms of symbolic communication. Dancing movements and sounds emitted by bees returning from foraging trips may only serve to attract the attention of hivemates so that they can be made aware of the odours associated with desirable food sites (6).
References:
(1) Wenner, A.M. 1971. The bee language controversy: an experience in science. Educational Programs Improvement Corporation, Boulder, Colorado, USA, 109 p.
(2) Goncalves, L.S. 1969. A study of orientation information given by one trained bee by dancing. J. apic. res. 8 (3): 113-132.
(3) Michener, C.D. 1974. The social behavior of the bees: a comparative study. Harvard University Press, Cambridge, USA, 404 p.
(4) Esch, H.E., S. Zhang, M.V. Srinivasan and J. Tautz. 2001. Honeybee dances communicate distances measured by optic flow. Nature 411: 581-583.
(5) Vadas, R.L. 1994. The anatomy of an ecological controversy: honey-bee searching behaviour. Oikos 69: 158-166 and at: http://www.beesource.com/pov/wenner/oikos94.htm
(6) O'Dea, J.D. 2000. Why do honeybees dance? naturalSCIENCE http://naturalscience.com/ns/nshome.html
(7) Esch, H, I.Esch and W.E. Kerr. 1965. Sound: An element common to communication of stingless bees and to dances of the honey bee. Science 149: 320-321.
(8) Nieh, J.C. 1998 The role of a scent beacon in the communication of food location by the stingless bee, Melipona panamica. Behav. Ecol. Sociobiol. 43: 47-58.
(9) Nieh, J.C. 1998. The food recruitment dance of the stingless bee, Melipona panamica. Behav. Ecol. Sociobiol. 43: 133-145.
(10) Nieh, J.C. and D.W. Roubik. 1998. Possible mechanisms for the communication of height and distance by a stingless bee, Melipona panamica. Behav. Ecol. Sociobiol. 43: 387-399.
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