Editing Bee learning and communication (section)

===Color learning in honeybees===
A number of experiments have demonstrated color recognition, discrimination and memory in honey bees ''[[Apis mellifera]]''. Beginning in the early 1900s, scientists [[Karl von Frisch]] and later Randolf Menzel began asking questions about color vision and various aspects of color learning in bees.<ref name=Carew2000>{{cite book|last=Carew|first=Thomas J.|title=Behavioral Neurobiology: The Cellular Organization of Natural Behavior|year=2000|publisher=Sinauer Associates|isbn=978-0-87893-084-5|chapter=9. Associative Learning in Honeybees}}</ref>

====Color discrimination====
[[Image:VonFrisch color vision experimental setup.jpg|thumb|alt=experimental design for testing color vision in honey bees.|Testing for color vision in honey bees. The majority of bees flew directly to the dish with the blue background as they had been trained to do. Thus, they were able to discriminate between gray and blue backgrounds, showing their capability for color vision.]]

The Austrian zoologist Karl von Frisch began the exploration of color vision in honey bees when, in 1919, he asked whether or not bees have  [[color vision]].  He performed an elegant experiment that showed not only that the bees could discriminate colors but that they demonstrated associative learning.<ref name="Carew2000"/> He first trained his bees to feed from a small dish filled with a nectar-like sugar water.<ref name="Carew2000"/> This dish was placed on a piece of blue colored cardboard so that the color was visible to the bees as they arrived at the dish and fed. Next, von Frisch placed identically sized pieces of cardboard in varying shades of grey, each with a dish, all around the blue piece.<ref name="vonFrisch">Frisch, K. von. 1956. Bees; their vision, chemical senses, and language. Ithaca, N.Y., Cornell University Press.</ref>  Lacking color vision, the bees should visit one or more of the gray pieces as often as the blue piece, but he found the vast majority of the bees flew directly to the blue piece of cardboard on which they had previously obtained their reward.<ref name="vonFrisch"/> The bees largely ignored the gray pieces which had not been rewarded.<ref name="vonFrisch"/> Von Frisch repeated the experiment with other colors like violet and yellow and got the same results.<ref name="Carew2000"/> Later other researchers used this experimental design to test the color vision of vertebrates.

====Color learning rates and preferences====
The German scientist Randolf Menzel continued the study of color vision in honey bees with more detailed tests. He was curious about whether bees would learn certain colors faster than others. He used lights of various color and intensity to project circles of light on a surface, a set-up like that used by von Frisch except that, by using light instead of cardboard, Menzel was able to easily change the intensity and color of the circles.<ref name="Carew2000"/> 
[[Image:Bee gathering pollen, Montreux.jpg|thumb|left|alt=bee collecting pollen.|Honey bee collecting pollen]]

To test bees ability to distinguish between two different colors, Menzel placed a small dish containing sugar-water in one circle and a second empty dish some distance away on a differently colored circle.  A single bee was placed equidistant between the two circles and allowed to choose between the dishes. The bees quickly learned to choose the color signaling the dish with the reward, and Menzel was able to measure how quickly the bees learned this task with various color differences.<ref name="Menzel">Menzel, R. and Backhaus, W. 1989. Color vision in honey bees: Phenomena and physiological mechanisms. In D. Stavenga and R. Hardie (eds): Facets of vision. Berlin-Heidelberg-New York: 281-297</ref>

Menzel's results showed that bees do not learn to discriminate between all color pairs equally well. Bees learned the fastest when violet light was rewarded, and the slowest when the light was green; the other colors fell somewhere in between. This evidence of inherent bias is evolutionarily reasonable, given that bees forage for differently-colored nectar-bearing flowers, many of which are to be found in green foliage which does not signal reward.<ref name="Carew2000"/><ref name="Menzel"/>

====Color memory====
After his work on color preferences, Menzel extended his experiments to study aspects of color learning and memory. He wanted to know how many trials bees need to reliably choose a previously rewarded color when they are presented with several alternatives, and how long they would remember the rewarded color.

Menzel did several experiments to answer these questions. First, he gave individual bees a single sugar reward on a colored background.  He then kept these bees in small cages for several days without any further trials. After a few days, he presented each bee with an array of several dishes, each on a different colored background. One of the colors was the same as that used during the initial trial, and the others were novel, unrewarded colors. Remarkably, after a single trial and several days without exposure to the rewarded color, bees correctly chose to explore the color used in the first trial more than fifty-percent of the time.<ref name="Carew2000"/><ref name="Menzel"/>

Menzel then repeated this experiment with another group of bees, keeping all factors the same except that in the second round of testing he gave the bees three initial trials with the rewarded color instead of just one. When, after several days in confinement, the bees were presented with a choice of colors they almost always chose the color that was used on the first three trials.<ref name="Menzel"/>

This ability to retain information about color-linked rewards for several days after minimal exposure to the rewarded color demonstrates the remarkable facility with which bees learn and retain color information.

====Timing in color learning====
In still other experiments, Menzel explored the timing of bee color learning by testing whether bees register color before, during, or after receiving their sugar-water reward. For this purpose Menzel displayed the color beneath a rewarded dish at different stages of the honey bee feeding process: during approach, feeding and departure.<ref name="Carew2000"/>

Menzel found that bees register color during both approach and feeding, and that they had to see the color for about a total of about 5 seconds, with best performance usually coming with about three seconds exposure during the approach and two seconds after landing and beginning to feed.<ref name="Menzel1991">Menzel, R. and Backhaus, W. 1991. Colour Vision in Insects. In P. Gouras (ed): Vision and Visual Dysfunction. The Perception of Colour. London: MacMillan Press, 262-288.</ref>