72 THE EYE IN EVOLUTION 



source of food to the position of the sun at the time, while the speed 

 of the dance varies inversely as the distance (about 10 revolutions in 

 15 sees, to indicate a distance of 100 metres, 2-5 revolutions to indicate 

 3,000 metres). The indications of direction attain an accuracy of 3° 

 in good conditions, of distance of up to 100 metres. Moreover, unlike 

 the ant, bees possess an innate time-keeping mechanism whereby they 

 can make compensation for the movements of the sun or changes in the 

 pattern of polarization in the sky as the day progresses, making the 

 appropriate correction in their direction (Fig. 46). 



It is interesting that there is no component in the dance for a vertical 

 distance, presumably because svich is rarely required in natural surroundings ; 

 and when von Frisch et al. (1953) fed bees on a feeding-table perched on a radio 

 beacon directly above the hive, new foragers were unable to find it. As performed 

 in the hive the waggle-rvin serves to indicate the direction of the food as related 

 to the sun by reference to the vertical as determined by gravity ; occasionally 

 the dance is performed on the horizontal alighting board in front of the hive 

 and in this case the waggle-run points to the actual direction of the feeding place 

 without reference to the sun. Moreover, in different localities different " dialects " 

 are used. Thus, while von Frisch (1950) found that Avistrian and German bees 

 dance in a circle to indicate food near at hand without giving any indication 

 of its direction, Tschumi (1950) and Baltzer (1952) found that Swiss bees, and 

 Hein (1950) that Dutch bees perform a "sickle dance", dancing in a semi-circle 

 the axis of which denotes the appropriate direction to be followed exactly in the 

 same way as the straight part of the figure-of-eight dance indicates this for far 

 distances (Fig. 45b). 



This extremely complex and highly ritualized pattern of behaviour 

 is an astonishing performance, particularly when it is recalled that the 

 brain of the bee is about one-tenth of an inch in diameter ; it is 

 apparently inborn and instinctive, but its precise implications have to 

 be learnt through experience by the young workers (Lindauer, 1952). 

 The response is disorientated in shadow, resumes its rhythm as soon 

 as a patch of blue sky becomes visible, and can be artificially changed 

 - by the interposition of a polarizing film between the insects and the 

 sun. Moreover, when trained bees are transported from the northern 

 to the southern hemisphere where the direction of the sun's movement 

 to an observer is anti-clockwise instead of clockwise, their foraging 

 movements tend to be reversed (Kalmus, 1956). A somewhat similar 

 or even more complicated " language " is used by scout bees to indicate 

 the position or direction for a suitable new home or swarm. 



It is clear, therefore, that the orientation of insects out-of-doors, although 

 determined by automatic responses, is an extremely complex affair influenced 

 by many stimuli acting sometimes singly, sometimes in combination ; and it 

 is equally clear that much work will require to be done before their behaviour is 

 fully elucidated, 



Aqnafir ■ rfhrojwds also make use of polarized light to orientate 

 themselves \^ ile swimming, in some cases reacting to the polarized 



