78 THE CASE OF PAPILIO POLYTES [ch. 



upper. The body remains black as in all the other 

 forms. This type of female bears a resemblance to 

 Papilio hector (PI. V, fig. 6), and for that reason we 

 shall speak of it as the H form. It should be added 

 that these three forms of female are quite indistinguish- 

 able in the larval and chrysalis stages. 



It was Wallace who first offered an explanation of 

 this interesting case in terms of mimicry. According 

 to this interpretation P. polytes is a palatable form. 

 The larva, which feeds on citronaceous plants, and the 

 chrysalis are both inconspicuous in their natural 

 surroundings. They may be regarded as protectively 

 coloured, and consequently edible and liable to per- 

 secution. The original coloration is that of the male 

 and the if female. From this the other two forms of 

 female have diverged in the direction of greater instead 

 of less conspicuousness, although the presumed edi- 

 bility of the insect might have led us to think that a 

 less conspicuous coloration would have been more to 

 its advantage. But these two females resemble the 

 two species Papilio aristolochiae and Papilio hector, 

 which, though placed in the same genus as P. polytes, 

 belong to a very different section of it^. The larvae 

 of these two species are conspicuously coloured black 

 and red with spiny tubercles. They feed upon the 

 poisonous Aristolochia plants. For these reasons and 

 also from the fact that the butterflies themselves are 

 both conspicuous and plentiful it is inferred that they 

 are unpalatable. In short, they are the models upon 



1 See Appendix II, p. 158. 



