The Making of Species 



These proportionate advantages are inversely in 

 the duplicate ratio of the respective percentages 

 that would have survived without the mimicry/ " 



This is rather a cumbrous method of saying 

 that if there are in a locality a number of young 

 birds, and each of these has to learn by ex- 

 perience which insects are edible and which are 

 not, each will, if it learns by one example, devour 

 one insect of any given pattern. Now, if two 

 species of inedible insects have this pattern, they 

 will between them lose only one member in the 

 educating process of each bird, whereas if each 

 species of insect had a colouration peculiar to 

 itself, each species would lose a whole individual 

 instead of half a one. There can be no doubt 

 that such a livery of unpalatability is of some 

 advantage to its possessors. 



It has been shown experimentally that hand- 

 reared young birds have to acquire their know- 

 ledge of flavours and colours by experiment. 



It is well known that in many species the 

 male and the female are not coloured alike. 

 Such species are said to exhibit sexual 

 dimorphism. In these cases it is usually 

 the male that is more conspicuously coloured. 

 Darwin felt that the theory of natural selection 

 could not satisfactorily account for this phe- 

 nomenon, so put forward the supplementary 

 theory of sexual selection. On this hypothesis 

 the females are supposed to be able to pick and 



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