The Making of Species 



by the same species " (Essays on Evolution, 



P- 372). 



Occasionally the female mimics two other 

 species, i.e. she occurs in two forms, each like 

 a different species. 



It sometimes happens that the female alone 

 mimics. This is said by Wallace to be due to 

 her greater need of protection. When she is 

 laden with eggs her flightjis slow, and therefore 

 she requires a special degree of protection. 



9. It is said that in some species we find a 

 non-mimetic ancestor preserved on islands where 

 the struggle for existence is less severe, while 

 on the adjacent continent mimicry has been 

 developed. 



10. It is alleged that in the cases where moths 

 resemble butterflies the former are either as 

 diurnal as the butterflies or are species which 

 " readily fly by day when disturbed." 



11. It is asserted that some seasonally di- 

 morphic forms are examples of mimicry only in 

 one state, in the form that comes into being at 

 the time when the struggle for existence is most 

 severe ; that is to say, in the dry season, in 

 Africa, when insect life is far less abundant than 

 in the rainy season. 



In other cases the mimicry of the dry- weather 

 form is said to be far more perfect. 



Instances of this phenomenon are set forth in 

 Professor Poulton's Essays on Evolution. 



230 



