vn] THE CASE OF PAPILIO POLYTES 81 



is relatively poorly developed in birds, and from this 

 we can only argue that the senses of smell and taste 

 are not especially acute. Really we can do little more 

 than to describe how these mimetic resemblances 

 appear to our own senses, and to infer that they do not 

 appear very different to the bird. If there is any 

 difference in keenness of perception we shall probably 

 not be far wrong in presuming that the advantage 

 rests with the bird. After all if there is any truth in 

 the theory of mimicry the bird has to depend largely 

 upon its keenness of sight in making its living, at 

 any rate if that living is to be a palatable one. If 

 natural selection can bring about these close resem- 

 blances among butterflies it must certainly be supposed 

 to be capable of bringing the bird's powers of vision to 

 a high pitch of excellence. 



Returning now to the case of P. polytes, there is 

 not the least doubt that to the ordinary man accustomed 

 to use his eyes the A form of female is easily distinguish- 

 able from P. aristolochiae, as also is the H form from 

 P. hector. The two models have a feature in common 

 in which they both differ from their respective mimics. 

 In both of them the body and head are largely of a 

 brilliant scarlet, whereas neither of the mimics has a 

 touch of red on the body. In the living insect when 

 the body is swelled by its natural juices the effect is 

 very striking^. It gives at once a "dangerous" look 



^ The specimens figured on PL V were dried in papers when taken. 

 The body is consequently much compressed and the characteristic 

 scarlet of P. hector and P. aristolochiae is largely hidden. 



P. M. 6 



