18 MR. A. R. WALLACE ON THE PAPILIONIDÆ 
own explanation. Mr. Bates has shown that certain groups of butterflies have a defence 
against insectivorous animals, independent of swiftness of motion. These are generally 
very abundant, slow, and weak fliers, and are more or less the objects of mimicry by 
other groups, which thus gain an advantage in a freedom from persecution similar to 
that enjoyed by those they resemble. Now the only Papilios which have not in Celebes 
acquired the peculiar form of wing belong to a group which is imitated both by other 
‚species of Papilio and by Moths of the genus Epicopeia, West. This group is of weak | 
and slow flight; and we may therefore fairly conclude that it possesses some means of 
defence (probably in a peculiar odour or taste) which saves it from attack. Now-the 
arched eosta and faleate form of wing is generally supposed to give increased powers of 
flight, or, as seems to me more probable, greater facility in making sudden turnings, and 
thus baffling a pursuer. . But the members of the Polydorus-group (to which belongs the 
only unchanged Celebesian Papilio), being already guarded against attack, have no need 
of this increased power of wing ; and “natural selection” would therefore have no tendency : 
to produce it. The whole family of Danaid: are in the same position: they are slow and 
weak fliers ; yet they abound in species and individuals, and are the objects of mimicry. 
The Satyridæ have also probably a means of protection—perhaps their keeping always 
near the ground and their generally obscure colours; while the Lycænidæ and Hesperidæ 
may find security in their small size and rapid motions. In the extensive family of the 
Nymphalidæ, however, we find that several of the larger species, of comparatively feeble 
structure, have their wings modified (Cethosia, Limenitis, Junonia, Cynthia), while the 
large-bodied powerful species, which have all an excessively rapid flight, have exactly 
the same form of wing in Celebes as in the other islands. On the whole, therefore, we 
may say that all the butterflies of rather large size, conspicuous colours, and not very 
swift flight have been affected in the manner described, while the smaller-sized and 
obscure groups, as well as those which are the objects of mimicry, and also those of 
exceedingly swift flight, have remained unaffected. 
It would thus appear as if there must be (or once have been) in the island of 
Celebes, some peculiar enemy to these larger-sized butterflies which does not exist, or is . 
less abundant, in the surrounding islands. Increased powers of flight, or rapidity of - 
turning, was advantageous in baffling this enemy ; and the peculiar form of wing necessary - 
to give this would be readily acquired by the action of * natural selection ” on the slight 
variations of form that are continually occurring. Such an enemy one would naturally - 
suppose to be 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 — 
Moluecas on the other ( Monarcha, khipidura), are almost entirely absent from Celebes. - 
Their place seems to be supplied by the Caterpillar:catchers (Graucalus, Campephaga), 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 t 
highly probable that they do so when other food is scarce*, 
fauna of Celebes is undoubtedly highly peculiar in every department of which we have 
* Mr. Bates has sugge 
they were more abundant in Celebes than elsewhere. 
he wing, but it is 
However this may be, the 
sted that the larger Dragon-flies (ÆsAna, &c.) prey upon butterflies; but I did not notice that — 
