In Message Mon, 3 May 1993 15:02:17 GMT, "Dr. M. Giurfa" <[log in to unmask]> writes: >Berlin, 3.5.93 >.. >.. >UV-Orientation: >.. > There is certainly a spectral pattern in the sky which depends on the >angular distance to the sun. As the radiant intensity of scattered light >is inversely proportional to the fourth power of wavelenght, the relative in- >tensity of short wavelenght radiation is higher in scattered skylight than >in direct sunlight. The opposite is valid for longer wavelenghts (this >sounds terrific!). >.. > To put it simply, if one imagines the sky over an observer, it should >be represented like a dome. In this dome, longer wavelenghts will be around >the solar spot whereas shorter wavelenghts will be mainly in the antisolar >meridian of the sky (the half part of the dome opposed to the sun). >.. > But what does mean "shorter" and "longer" wavelenghts for the bees' >eye? After the comments on this topic that we got, we know that bees can see >colours, from UV (the shortest wavelenght they can see) until green (the >longer wavelenght they can see). In other words, with a little bit from >imagination, the sky dome should appear to the bees like an UV dome with a >green sun. To prove that this is not only a Sci-Fi exercise, people like >Samuel Rossel (Freiburg, Germany) and Ruediger Wehner (Zurich, Switzerland) >raised the question of the use of spectral patterns in the orientation stra- >tegies of honeybees. >.. > They asked, for example, whether UV as a colour is used in a particu- >lar orientation strategy. They trained bees to a known food source and then >they recorded the dances of the foragers once in the hive. Bees danced >on an horizontal surface and were covered by a plexiglass dome (they could not >see neither the sky nor the sun through it). A hole was opened in the dome and >a spot of UV light was offered there. Dances were recorded and deviations of >the correct direction to the food source measured. It was promptly demons- >trated that bees can actually use UV as an orientation cue but in a BROAD >WAY and not in a fine way (as wrongly suggested by a previous mail): BEES >INTERPRETED AN UV SPOT AS LYING ANYWHERE WITHIN THE ANTISOLAR HALF OF >THE SKY. That means that, when bees see an UV patch, "they know" that they >are looking in the antisolar half of the sky. With the same kind of >experiments, it was demonstrated that ANY GREEN SPOT is taken for the sun >and dances are reoriented accordingly. >.. > To summarize it, spectral information can be used in a broad orien- >tation strategy. A green spot represents the sun whereas an UV spot repre- >sents a patch lying anywhere within the half of the sky opposed to the sun. >.. > If somebody wants to read more about this, I would recommend "The >bee's celestial compass" from Ruediger Wehner, in "Experimental behavioural >Ecology and Sociobiology"(Hoelldobler & Lindauer eds), G Fischer, 1985. >.. > Finally, a personal request. I think that contributions to the net >based on popular beliefs or some kind of mystical knowledge do not help but >simply add to a great confusion. So, I would like to have comments based on >scientific literature and on replicated experiments. I hope that this does >not sound aggressive. I only believe that this is the way in which all the >people can really benefit from the net. >.. > Cheers, >.. >.. > Martin Giurfa >.. > Institute fur Neurobiologie > Freie Universitaet Berlin > Koenigin-Luise-Str. 28/30 > 1000 BERLIN 33 - GERMANY >.. > [log in to unmask] >.. >..Very good suggestion ! Harald Esch Department of Biological Sciences University of Notre Dame =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Harald E. Esch ("[log in to unmask]") Professor, Dept. Biological Sciences University of Notre Dame, Notre Dame IN 46556 Phone: (219) 631-7025 FAX: (219) 631-7413 Dept. Office: (219) 631-7186 =-=-=-==-=-==-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=