ILLUSTRATIVE OF NATURAL SELECTION. 177 



an insectivorous bird ; but it is a remarkable fact that 

 most of the genera of Fly-catchers of Borneo and Java 

 on the one side (Muscipeta, Philentoma,) and of the 

 Moluccas on the other (Monarcha, Ehipidura), are 

 almost entirely absent from Celebes. Their place seems 

 to be supplied by the Caterpillar-catchers (Grauca- 

 lus, Campephaga, &c.), of which six or seven species 

 are known from Celebes and are very numerous in 

 individuals. We have no positive evidence that these 

 birds pursue butterflies on the wing, but it is highly 

 probable that they do so when other food is scarce. 

 Mr. Bates has suggested to me that the larger Dragon- 

 flies (^Eshna, &c.) prey upon butterflies ; but I did not 

 notice that they were more abundant in Celabes than 

 elsewhere. However this may be, the fauna of Celebes 

 is undoubtedly highly peculiar in every department of 

 which we have any accurate knowledge ; and though we 

 may not be able satisfactorily to trace how it has been 

 effected, there can, I think, be little doubt that the 

 singular modification in the wings of so many of the 

 butterflies of that island is an effect of that complicated 

 action and reaction of all living things upon each other 

 in the struggle for existence, which continually tends 

 to readjust disturbed relations, and to bring every 

 species into harmony with the varying conditions of 

 the surrounding universe. 



But even the conjectural explanation now given fails 

 us in the other cases of local modification. Why the 

 species of the Western islands should be smaller than 

 those further east, why those of Amboyna should 



IT 



