OF THE MALAYAN REGION. 21 



very clearly that their life is an easy one, and that they are free from persecution hy the 

 foes which keep down the population of less favoured races. This superabundant popula- 

 tion has been shown by Mr. Bates to be a general characteristic of all American groups 

 and species which are objects of mimicry ; and it is interesting to find his observations 

 confirmed by examples on the other side of the globe. 



The remarkable genus Drusilla, a group of i:)ale-coloured butterflies, more or less 

 adorned with ocellate spots, is also the object of mimicry by three distinct genera 

 [Melanitis, Sijantis, and Papilio). These insects, like the Danaidce, are abundant 

 in individuals, have a very weak and slow flight, and do not seek concealment, or 

 appear to have any means of protection from insectivorous creatures. It is natural to 

 conclude, therefore, that they have some hidden property which saves them from attack ; 

 and it is easy to see that when any other insects, by what we call accidental variation, 

 come more or less remotely to resemble them, the latter will share to some extent in 

 their immunity. An extraordinary dimorphic form of a female Fcqnlio has come to 

 resemble the Drusillas sufiiciently to be taken for one of that group at a little distance ; 

 and it is curious that I captured one of these Papilios in the Aru Islands hovering along 

 the ground, and settling on it occasionally, just as it is the habit of the Drusillas to do. 

 The resemblance in this case is only general ; but this form of Papilio varies much, and 

 there is therefore material for natural selection to act upon so as ultimately to pro- 

 duce a copy as exact as in the other cases. 



The eastern Papilios allied to Polydorus Coon and P. Phlloxenus, form a natural section 

 of the genus resembling, in many respects, the ^weas-group of South America, which 

 they may be said to represent in the East. Like them, they are forest insects, have a 

 low and weak flight, and in their favourite localities are rather abundant in individuals ; 

 and like them, too, they are the objects of mimicry. We may conclude, therefore, that 

 they possess some hidden means of protection, which makes it useful to other insects to 

 be mistaken for them. 



The Papilios which resemble them belong to a very distinct section of the genus, in 

 which the sexes differ greatly; and it is those females only which differ most from 

 the males, and which have already been alluded to as exhibiting instances of dimorphism, 

 which resemble species of the other group. 



The resemblance of P. Romulus to P. Sector is, in some specimens, very considerable, 

 and has led to the two species being placed to foUow each other in the British Museum Ca- 

 talogues and by Mr. E. Doubleday. I have shown, however, that P. Romulus is probably a 

 dimorphic form of the female P.Pmnmon, and belongs to a distinct section of the genus*. 



The next pair, P. Theseus, Cr., and P. Antipkus,'E<i\i., have been united as one sj)ecies 

 both by De Haan and in the British Museum Catalogues. The ordinary variety of P. 

 Tlieseus found in Java almost as nearly resembles P. Diphilus, Esp., of the same country. 

 The most interesting case, however, is the extreme female form of P. Ilemnon (P. Achates, 

 Cr.) t, which has acquired the general form and markings of P. Coon, an iasect which differs 

 from the ordinary male P. Memnon, as much as any two species differ which can be chosen 

 in this extensive and highly varied genus ; and, as if to show that this resemblance is not 

 accidental, but is the result of law, when in India we find a species closely allied to 

 * See Plate II. fig. 6. f See Plate I. fig. 4. 



