* MR. A. R. WALLACE ON THE PAPILIONID.E 



sometimes even straying into the narrow bazaars or covered markets of the city. In 

 Java the goldcn-dustcd Ary una may often be seen at damp places on the roadside in the 

 mountain districts, in company -with Sarpedon, Bathycles, and Agamemnon, and less fre- 

 quently the beautiful swallow-tailed Antiphates. In the more luxuriant parts of these 

 islands one can hardly take a morning's walk in the neighbourhood of a town or village 

 without seeing three or four species of Papilio, and often twice that number. No less 

 than 120 species of the family are now knoAvn to inhabit the Archipelago, and of these 

 ninety-six were collected by myself. Twenty-nine species are found in Borneo, being the 

 largest number in any one island, twenty-three species having been obtained by myself 

 in the vicinity of Sarawak ; Java has twenty-seven species ; Celebes and the Peninsula 

 of Malacca twenty-three each. Further east the numbers decrease, Batchian producing 

 seventeen, and New Guinea only thirteen, though this number is certainly too small, 

 owing to our present imperfect knowledge of that great island. 



In estimating these numbers I have had the usual difficulty to encounter, of determining 

 what to consider species and what varieties. The Malayan region, consisting of a large 

 number of islands of generally great antiquity, possesses, compared to its actual area, a 

 great number of distinct forms, often indeed distinguished by very slight characters, but 

 in most cases so constant in large series of specimens, and so easily separable from each 

 other, that I know not on what principle we can refuse to give them the name and rank 

 of species. One of the best and most orthodox definitions is that of Pritchard, the great 

 ethnologist, who says, that " separate origin and distinctness of race, ecinced by a con- 

 stant transmission of some characteristic peculiarity of organization,'^ constitutes a species. 

 Now leaving out the question of " origin," which we cannot determine, and taking only 

 the proof of separate origin, " the constant transmission of som,e characteristic peculiarity 

 of organization," we have a definition which will compel us to neglect altogether the 

 amount of difference between any two forms, and to consider only whether the differences 

 that present themselves are permanent. The inile, therefore, I have endeavoured to adopt 

 is, that when the difference between two forms inhabiting separate areas seems quite 

 constant, when it can be defined in words, and when it is not confined to a single pecu- 

 liarity only, I have considered such forms to be species. "V\Tien, however, the indiA-iduals 

 of each locality vary among themselves, so as to cause the distinctions between the two 

 forms to become inconsiderable and indefinite, or where the differences, though constant, 

 are confined to one particular only, such as size, tint, or a single point of difference in 

 marking or in outline, I class one of the forms as a variety of the other. 



I find as a general rule that the constancy of species is in an inverse ratio to their range. 

 Those which are confined to one or two islands are generally very constant. When they 

 extend to many islands, considerable variability appears ; and when they have an exten- 

 sive range over a large part of the Archipelago, the amount of unstable variation is very 

 large. These facts are explicable on Mr. Darwin's principles. When a species exists 

 over a wide area, it must have had, and probably still possesses, great powers of disper- 

 sion. Under the different conditions of existence in various portions of its area, different 

 variations from the type would be selected, and, were they completely isolated, would soon 

 become distinctly modified forms ; but this process is checked by the dispersive powers 



