vii] THE CASE OF PAPILIO POLYTES 83 



heavy and lumbering up-and-down flight. One gets 

 the impression that all the wing surface is being used 

 instead of principally the fore wings as appears in 

 P. hector and P. aristolochiae. The difference is difficult 

 to put into words, but owing to these peculiarities of 

 flight the eye has no difficulty in distinguishing between 

 model and mimic even at a distance of 40 to 50 yards. 

 Moreover, colour need not enter into the matter at all. 

 It is even easier to distinguish model from mimic when 

 flying against a bright background, as for instance when 

 the insect is between the observer and a sunlit sky, 

 than it is to do so by reflected light. I have myself 

 spent many days in doing little else but chasing polytes 

 at Trincomalee where it was flying in company with 

 P. hector, but I was never once lured into chasing the 

 model in mistake for the mimic. My experience was 

 that whether at rest or flying the species are perfectly 

 distinct, and I find it difficult to imagine that a bird 

 whose living depended in part upon its ability to dis- 

 criminate between the different forms would be likely 

 to be misled. Certainly it would not be if its powers 

 of discrimination were equal to those of an ordinary 

 civilised man. If the bird were unable to distinguish 

 between say the A form of female and P. aristolochiae 

 I think that it would be still less likely to distinguish 

 between the same A form and the male or the M form 

 of female. For my experience was that at a little 

 distance one could easily confuse the A form of 

 polytes with the male. Except when one was quite 

 close the red on the A form was apt to be lost, the 



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