chap, xvm.] OF CELEBES. 437 



facilities of distribution tend to assimilate the productions 

 of adjacent lands in two ways : first, by direct mutual 

 interchange of species ; and secondly by repeated immi- 

 grations of fresh individuals of a species common to other 

 islands, which by intercrossing, tend to obliterate the 

 changes of form and colour, which differences of condi- 

 tions might otherwise produce. Bearing these facts in 

 mind, we shall find that the individuality of the insects 

 of Celebes is even greater than we have any reason to 

 expect. 



For the purpose of insuring accuracy in comparisons 

 with other islands, I shall confine myself to those groups 

 which are best known, or which I have myself carefully 

 studied. Beginning with the Papiliomdae or Swallow- 

 tailed butterflies, Celebes possesses 24 species, of which the 

 large number of 18 are not found in any other island. If 

 we compare this with Borneo, which out of 29 species has 

 only two not found elsewhere, the difference is as striking 

 as anything can be. In the family of the Pieridse, or white 

 butterflies, the difference is not quite so great, owing 

 perhaps to the more wandering habits of the group ; but 

 it is still very remarkable. Out of 30 species inhabiting 

 Celebes, 19 are peculiar, while Java (from which more 

 species are known than from Sumatra or Borneo), out of 

 37 species has only 13 peculiar. The Danaidee are large, 

 but weak-flying butterflies, which frequent forests and 



