136 THE VALUE OF COLOUR 



by this fact. In order adequately to discuss the 

 question of Mimicry and sex it would be necessary 

 to analyse the whole of the facts, so far as they 

 are known in butterflies. On the present occasion 

 it is only possible to state the inferences which 

 have been drawn from general impressions — in- 

 ferences which it is believed will be sustained by 

 future detailed inquiry. 



(1) Mimicry may occasionally arise in one sex 

 because the differences which distinguish it from 

 the other sex happen to be such as to afford 

 a starting-point for the resemblance. Here the 

 male is at no disadvantage as compared with 

 the female, and the rarity of Mimicry in the 

 male alone (e. g. Cethosia) is evidence that the 

 great predominance of female Mimicry is not 

 to be thus explained. 



(2) The greater colour-variability of the female, 

 observed at least in certain groups of butterflies, 

 and especially her more pronounced tendency 

 to dimorphism and polymorphism, have been 

 of much importance in determining this pre- 

 dominance. Thus if the female appear in two 

 different forms and the male in only one, it will 

 be twice as probable that she will happen to 

 possess a sufficient foundation for the evolution 

 of Mimicry. 



(3) The appearance of melanic or partially 

 melanic forms in the female has been of very 

 great service, providing as it does a change of 

 ground-colour. Thus the Mimicry of the black 



