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ANNO 4 Numero 3
Jurgen Tautz [1]
What do honeybees know about flowers?

[1] Beegroup Würzburg, Biozentrum, Universität Würzburg, Am Hubland, D-97074, Würzburg

Corresponding author: tautz@biozentrum.uni-wuerzburg.de

What honeybees see and what they smell, their ability to orientate and a large proportion of their communication system is linked to their relationship with flowers.

What do bees need to know about flowers? And how do they get their knowledge? Knowledge can have three different origins: it can be genetically fixed, it can be acquired by experience (learning) and it can be transmitted through communication. All three mechanisms are realized in honeybees.

In order to study the complex achievement of honeybees in finding and exploiting flowers, it is helpful to divide their flower-visiting behaviour into functionally separate steps: bees have to recognize flowers as flowers; they have to distinguish between different flowers; to assess the nectar-state of the flowers; to know how to manipulate the different shaped flowers using their legs and mouthparts; to determine the geographical position of flowers and the times they are nectar-producing; to communicate their experience about flowers to nest-mates and make use of the information they receive from forager bees. Each of these steps is the object of intensive research, providing new insights and new interpretations of old observations.
The visual sense of the honeybees, poor in recognizing flowers over a distance, is essential in determining direction and distance of their flights between nest location and food source. The position of the sun and polarized light pattern on the sky gives information on the direction, the optic flow during flight measures distances of the flight track. These details of flight routes are transmitted to recruited bees by the bee dances inside the dark hive.

This dance communication, however, is loaded with deficiencies which blur the message considerably and make it imprecise. Furthermore, correlations do not prove causal relationships. Therefore, it was intensely debated whether and how much of the information that a human observer can read from a waggle dance is actually used by the follower bees. The arguments ranged from "it is an abstract language" to "they use nothing but are stimulated by the dance to simply search for the source of the scent that a dancer bee carries". It turned out that the truth is a combination of both assertions.

The dance transmits information and aids in the field are given to pinpoint the goals. If forager bees are forced
to fly through narrow tunnels that produce a high rate of optic flow, one can create “lying” bees. These bees dance for a location that is different from the one they actually found, by performing a waggle phase for more than 30 times the distance they had really flown. Observing the recruits, it becomes clear that they do not fly to the forager's real site, but they can be caught in an area around the spot indicated by the dance. Thus, the dances recruit followers in roughly the correct area.

Because the distance communicated depends on the optic flow that a landscape offers to the bees, it is clear that bees do not communicate distance as an absolute quantity. However, as long as follower bees fly out in the same direction as the dancer, the “mistakes” that both bees make are the same and cancel each other out.

However, non-manipulated dancers also send recruits not to a spot, but into a larger area. This area has an almost constant size independent of the distance from the hive. The reason for this is that the directions of consecutive waggle phases are not perfectly identical but show a certain degree of deviation. This deviation is smaller the further away the food source is. Consequently the follower bees are scattered across a wider range which makes more sense than having all bees that followed a dance go to one flower. The identification of flowers in the area that bees have been sent to is thus easy to accomplish when recruited bees follow the scent of flowers.