to draw your attention is this : while in Java, Sumatra, the 

 Malay Peninsula, India, etc., one of the several females is 

 tailed, there is no tailed memnon-^ on Borneo; the Bornean 

 form which corresponds to the tailed one of Sumatra has 

 i:)reserved the pattern distinctive of the tailed $, but the tail 

 has been lost entirely. 



Now let us for a moment consider geographically separated 

 varieties of Lepidoptera from quite a different point of view. 

 Along the west coast of Sumatra there is a chain of islands 

 each of which has its own, numerous, races of Lepidoptera, 

 many of the races being markedly different from those found 

 on Sumatra. On the other hand, the Natuna Islands between 

 Borneo and the Malay Peninsula are farther from Borneo 

 than, for instance, Nias is from Sumatra, yet their Lepidoptera 

 do not exhibit such conspicuous modifications as do those of 

 Engano, Mentawei, Nias, etc. What is the reason for this 

 difference in the degree of variation ? The insects in question 

 being the same species, the cause of their greater modification 

 on the one group of islands than on the other must be sought 

 for in the nature of the islands, using the word nature in the 

 widest sense, including the age of the islands. Entomologists 

 know very well that a geographically old district sej)arated 

 by sea or low lands from the nearest geologically old district 

 has its own geographical races. The modifications in the 

 species may refer either to colour, size, shape, or structure, or 

 to all, the species not reacting all in the same way. That is to 

 say, geographical variation also depends on the nature of the 

 insect. If we see it stated that a certain species has a very 

 wide distribution, but does not exhibit any geographical 

 variation, at once the explanation forms itself in our mind 

 either that the species is carried frequently from place to 

 place by the power of its wings or some other means, or that 

 the species has not been carefully studied. And in most 

 instances we find that nature has not made an exception, but 

 that the systematist has made a mistake. 



We have briefly considered first variation in one and the 

 same locality and then variation in different localities, and 

 now this question presents itself : are the varieties, whether 

 local or geographical, all of the same value as regards evolution i 



