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 persecution. The original coloration is that of the male and the M female. From this the other two forms of female have diverged in the direction of greater instead of less conspicuousness, although the presumed edibility 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[40]. 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 {79} which the two _polytes_ females that are unlike the male have been built up by natural selection. The suggestion of mimicry in this case is supported by the fact that there is a general correspondence between the areas of distribution of model and mimic. _P. hector_ is not found outside India and Ceylon, and the H female of _P. polytes_ is also confined to this area. _P. aristolochiae_, on the other hand, has a much wider range, almost as wide indeed as that of _P. polytes_ itself. Generally speaking the A female accompanies _P. aristolochiae_ wherever the latter species is found. Beyond the range of _P. aristolochiae_, in northern China, the M female alone is said to occur. On the other hand, as the matter comes to be more closely studied exceptions are beginning to turn up. The H female, for instance, is found on the lower slopes of the Himalayas, far north of the range of _P. hector_, and there are indications that a careful study of the distribution in China and Japan may prove of importance.