172 THE WORLD OF LIFE CHAP. 



true state of the case is rendered almost certain by the 

 occurrence of a large number of species in which the markings 

 for recognition are now unnecessary though they were of the 

 highest importance during the initial stages of evolution. 



Another and still more curious result of the study of this 

 subject is the evidence it affords that the most varied in 

 colour and markings of all insects the butterflies do not, 

 primarily, recognise each other by sight, but by some sense 

 analogous to that of smell. This seems now to be almost 

 certain, and it affords the explanation of what would other- 

 wise be a great difficulty, how the males of polymorphic 

 females, as in Papilio pammon in the East and Papilio <zneas 

 in the West, numerous American Pieridae and many other 

 groups, in which the females are coloured as if with the 

 purpose of being as unlike their mates as possible, are able 

 to recognise each other. Intuitive knowledge or " instinct " 

 is now given up by every thinker ; but the proof now given 

 that the only known method of mutual recognition by Lepi- 

 doptera is by scent, explains the whole difficulty. The 

 colours and markings of these insects have been produced in 

 adaptive relation to their enemies almost exclusively, and 

 this explains the fact that the strangely diverse females 

 above referred to are, probably in every case, either protectively 

 coloured or mimics of distasteful forms in their own district. 

 The fact that several of the Eastern Papilios have fully 

 tailed females while they themselves are round-winged, is 

 another indication that sight can have no part in leading to 

 mutual recognition between the sexes. 



The almost universal presence of some form of recognition- 

 marks in birds and mammals, no less than the proof now 

 afforded (and for the first time stated) of their entire absence 

 in the Lepidoptera, affords, I think, ample justification for 

 the importance I claim for them, and for the space I have 

 devoted to them in the present volume. 



