Upon her return from a foraging flight a bee might behave quite strangely: she throws her body from side to side moving wildly over the comb surface. Others attend this performance and – after a little while – show up at her feeding site. The so called “waggle dance” informs nestmates about the existence and the location of valuable ressources like food and water. Honeybees are the only species in the insect world showing an abstract – we might call it symbolic – communication.
More than 60 years after the discovery of the meaning of the dance many questions remain unanswered. How do the follower bees decode the dance? Which stimuli sent out by the dancer carry information and which are actually used by the receivers of the message?
Therefor, the research groups of Prof. Dr. Menzel (Institute of Neurobiology) and Prof. Dr. Landgraf (Institute of Computer Science) are studying the dance communication in Apis mellifera bees by means of a robotic honeybee, aka the Project RoboBee.
The Waggle Dance
Karl von Frisch discovered that a highly stereotypical motion pattern that honeybees perform on the comb surface conveys to a human observer the circular coordinates (direction and distance) of relatively well-defined locations. The term ‘waggle dance’ denotes a form of this pattern which conveys information on targets located fairly far from the hive. It is embedded in a series of communication systems enabling a honeybee colony to coordinate the activity of its members during foraging and nest-site selection.
The video above shows a waggle dancing forager in slow motion.
In the waggle dance, a successful forager moves forward on the comb surface while wagging its abdomen from side to side at about fifteen times per second. This straight portion of the dance is called a ‘waggle-run’. Without interruption, it moves in a semicircular trajectory and returns to the starting point of the last waggle-run. This portion is called a ‘return-phase’, and the dancer tends to alternate clockwise and counter clockwise throughout successive return-phases. Once at this position, it repeats the forward, wagging portion of the dance. The entire motion pattern is strongly linked to the dancer’s recent navigation experience. First, flying bees use the sun as a reference to maintain a course, and the average orientation of a dancer’s successive waggle-runs relative to the direction of gravity approximates the angle between the direction toward the goal and toward the sun. Second, honeybees gauge the distance they travel (most likely by integrating self-induced optic flow during flight, i.e., the net amount of image motion over the retina accumulated during movement), and the average length of the waggle-runs increases together with the flown distance. The waggle dance is thus an intriguing example of multisensory convergence, central processing, transformation between sensory modalities and motor coordination that contains indexical information for the follower bee about the indicated location.
This video gives a good summary:
The Honeybee Robot
We have developed many different prototypes of a mechanical model of a dancing honeybee. The recent prototypes are based on a simple plotter design. The bee replica is moved in a plane by two motors and rotated by a third. Numerous stimuli can be produced by the model: Heat, wing oscillations, air flows, sounds, scents and more. And it can move in the typical waggle dance shape.
This video shows a robotic dance – followed by a honeybee.
The robot carries two micro-cameras that enable it to prevent collisions. The cameras are used to recognize also those bees that might be interested in a sugar sample that can be delivered promptly by the robot.
Dept. of Biology, Pharmacy and Chemistry / Institute of Neurobiology / Free University Berlin
Dept. of Mathematics and Computer Science / Institute of Computer Science / Free University Berlin
with the help of many, many students!
The project was funded by the German Research Foundation (DFG) and the German Ministry of Education and Research (BMBF).