Insects and their world 



two or more equally dangerous or unpalatable insects. As Imms puts it 

 (1947)5 if a species has to lose '500 individuals before its enemies learn 

 that it is unpalatable, then it is an obvious advantage for two species 

 to look alike, and hence to lose only 250 each. This is called Mullerian 

 mimicry. Obviously both species must be unpalatable, or dangerous, 

 and you do not have a model and a mimic as in Batesian mimicry. 



As an argument, this is somewhat less convincing than the theory of 

 Batesian mimicry, but it is an observed faa that there are certain con- 

 spicuous patterns of warning colouration that are shared by a variety of 

 different insects. 



This is not the whole of the story. When you study insects from 

 different parts of the world you find that the insects — or at least the 

 bigger and more shov^^ ones — of each continent have something alike 

 in their appearance. It is hard to say exactly what this is. Perhaps there 

 is a tendency for many of the insects of one continent to repeat the same 

 shades of colour, rather in the way that you can recognise the work of 

 some artists by their fondness for a particular shade of mauve, or blue- 

 green. An experienced entomologist can often look at a box of insects 

 and successfully guess whether they came from Africa, or South 

 America, or the Far East, just by their general colour. 



It is evident that the evolution and natural selection of shape, colour 

 and pattern is a subtle process, which is as yet imperfectly understood. 



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