OF THE MALAYAN REGION. 21 
very clearly that their life is an easy one, and that they are free from persecution by 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 pale-coloured butterflies, more or less 
adorned with »ocellate spots, is also the object of mimicry by three distinct genera 
(Melanitis, Hyantis, and Papilio). These insects, like the Danaide, 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 dimorphie form of a female Papilio has come to 
resemble the Drusillas sufficiently 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. Philoxenus, form a natural section 
of the genus resembling, in many respects, the Æneas-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. Hector is, in some specimens, very considerable; 
and has led to the two species being placed to follow each other in the British Museum Ca- 
talogues and by Mr. E. Doubleday. I have shown, however, that P. Romulus is probably a 
dimorphie form of the female P. Pammon, and belongs to a distinct section of the genus*. 
The next pair, P. Theseus, Cr., and P. Antiphus, Fab., have been united as one species 
both by De Haan and in the British Museum Catalogues. The ordinary variety of P. | 
Theseus 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. Memnon (P. Achates, 
Cr.) t, which has acquired the general form and markings of P. Coon, an insect 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 
| pee but is the result of law, when in India we find a species closely allied to 
* See Plate II. fig. 6. + See Plate I. fig. 4. 
