Biological Inspiration - Bees • Introduction • “The Dance Language and Orientation of Bees,” Karl von Frisch • More Recent Developments • References Jun Goo, Autonomous Multirobot Systems, October 12, 1999
Introduction Why do people study bees?
Economic Importance in Agriculture • Economic reasons: they play a critical role in U.S. agriculture • Value of crops requiring bee pollination estimated to be around $24 billion each year • Commercial bee pollination valued around $10 billion annually • USDA pays for research aimed at the improvement of honey bee pollination of fruit and seed crops and ecologically important plant species United States Department of Agriculture Agricultural Research Service
Interesting focus of research “Honey bees pose an interesting puzzle to biologists because they exhibit astonishing adaptive flexibility in their responses to features of their environment, and yet have exceedingly small nervous systems with which to handle the relevant sensory information. The juxtaposition of behavioral complexity and neural simplicity raises the hope of insights into the design features by which nervous systems can efficiently encode and store information about the outside world, and into evolutionary principles by which such behavioral abilities could have arisen.”
Why do people study bees? • Communication: How do they inform other bees of food sources which can be up to more than 10 km away? • Recognition:How are they able to distinguish nestmates from other bees? Or landmarks? • Orientation:How do they know where they are or where they are going? • Social behavior, division of labor • Aerodynamics, neurobiology, chemistry, genetics, evolutionary biology, ...
The Dance Language and Orientation of BeesKarl von Frisch (1967) • For many centuries, naturalists had observed that honeybees were able to tell their nestmates about discoveries they make beyond the hive but the system of communication that the insects used remained a mystery • 1940s, Von Frisch (University of Munich) was the first person to really examine and discover the significance of the bee dance in communication
Communication through Dance Language • The Round Dance • The Tail-Wagging Dance
Method used by foraging bees to communicate to others about nearby food sources Von Frisch provides a description of how this communication takes place. The Round Dance as Communication
Case 1: The objective is known to a group of bees • A group of marked worker bees collecting from a source (a dish containing sugar water) stop making regular flights once the dish runs dry and simply return and sit around in the hive • They still continue to scout the feeding place, often at first but with more spread out intervals later. All bees in the group are involved in the scouting but with differing levels of “individual zeal” • The dish is refilled and a scouting bee returns with a stomach full of honey, “makes a lively and excited run up the comb” and feeds the others with the sugar solution
The bee then goes through a series of movements describes as the round dance which arouses the interest of the bees around her. If group members were among those who were following her, they now fly out back to the feeding place. Once they return, they also perform the dance. This way, the entire group is notified and back in action. Case 1: The objective is known to a group of bees
Case 1: The objective is known to a group of bees • A returning food-distributing bee was also able to cause group members with whom she came in contact with to revisit the feeding place without dancing. This happened about 40 percent of the time whereas contact plus dancing had been effective about 90 percent of the time. • If two different groups were collecting at different dishes and one of the dishes was refilled after an interruption in feeding, then the bees of the second group would also be induced into action by the dances of the successful group and would keep returning to examine their empty dish. This showed that the bees in a given group were not personally known to one another.
Case 2: The objective is not known to the bees • A bee discovers a source of food and through the round dance recruits helpers who are unfamiliar with the location of the food source. • Similar situation occurs when members of a group who have found their food site to be replenished start performing the round dance and attract newcomers. Newcomers only join when there is dancing and the number that join depend on the number of dancers and the liveliness of the dancing. • The liveliness and number of the dances depends upon the profitability of the food source. This is mainly determined by the quantity and sweetness of the sugar solution. • Newcomers alerted by round dances search the vicinity in all directions • Also may be influenced by olfactory cues of dancing bees: search for flowers with the specific odor
The Tail-Wagging Dance • When food is more than 100 m from hive, round dance is replaced by tail-wagging. • Tail-wagging also provides information as to the distance and direction of the goal. • More complex than round dance.
Factors Determining the Release and Liveliness of the Dances • Sweetness of Sugar Solution • distension of the honey stomach shown to be unrelated to dancing level • sorbitol experiment revealed dancing released solely or primarily through direct sense of taste • change in sound production during waggling with higher sugar concentration though no evidence that higher sound was registered by nestmates as sign of better food • Purity of Sweet Taste • salt added • hydrochloric acid, quinine
Factors Determining the Release and Liveliness of the Dances • Ease of Obtaining the Solution • quantity appears important • unsure as to how this was measured. Von Frisch suggests time since longer times appeared to decrease dancing. • Viscosity • would mean more work and longer time. • trisaccharide raffinose • increases the liveliness of dances. Under natural circumstances, increased viscosity tends to correlate to richer sugar.
Factors Determining the Release and Liveliness of the Dances • Load • Added weight accompanied by somewhat increased flight time. • Eagerness to dance not only undiminished but frequently clearly increased. • Again, under natural circumstances, increased weight associated with higher sugar content of nectar • Proximity • Appears that bees dance for the same length of time • Nearness allows closer bees to repeat dances more frequently
Factors Determining the Release and Liveliness of the Dances • Floral Fragrance + Form of Container • floral scents increased liveliness of dances • narrow tubes and clefts also resulted in increased dancing • Uniform Flow • food source must be continuous, bees do not dance after first flight • exceptions: great need, moderate shortage, unusual good find • Status of Nourishment in Colony • food supply (seasonal + storage) • famine, immediate dancing • Relativity • percentage of dancing foragers greater when 0.5M sucrose given after 0.25M solution then 0.5M solution given after 1M solution
Factors Determining the Release and Liveliness of the Dances • Time of Day • Flight intensity drops temporarily around noon • Attributes this to diurnal periodicity in activity widely known among insects and other animals • Weather • take into account weather conditions in foraging • several hours prior to storm, bees foraging from nearby sources continued to dance and forage while dancing for bees which were travelling to a source 6 km away declined rapidly and eventually stopped • bees to nearby source kept foraging until storm actually broke
Regulation of Supply and Demand on the Flower Market • Dance releases factors combined together result in a regulated exploitation of the sources of food in accordance with their profitability • Scouts only signal nestmates for worthwhile sources of food • Each individual bee concentrates on a relatively small area which it visits again and again. Economy of labor and limits unnecessary searching. • Different species of plant are very distinct in their supply of nectar and its sugar content. Good sources of food are exploited more intensively. Likewise, when food supply runs out, bees may stay until situation improves or may stay home to avoid unnecessary risk in flight. • Bees are able to adapt to diurnal variations
Orientation and Other Topics Half the book is devoted to the dance language and how it relates to foraging. The other half deals with orientation and how bees are able to navigate from the hive to a foraging spot and back to the hive. Also mentions danceless communication in a couple pages in the middle of the book. Kirchner and Towne demonstrate that sound is an important part of the dance language by using a robotic bee to simulate dancing which a foraging bee would have produced.
References Books: Lindauer, Martin. (1971). Communication Among Social Bees. Cambridge, Massachusetts: Harvard University Press. Seeley, Thomas D. (1995). The Wisdom of the Hive: The Social Physiology of Honey Bee Colonies. Cambridge, Massachusetts: Harvard University Press. Von Frisch, Karl. (1967). The Dance Language and Orientation of Bees. Cambridge, Massachusetts: Harvard University Press. Links: http://www.sciam.com/0694issue/0694kirchner.html http://www.cyberbee.net