18 MR. A. R. WALLACE ON THE PAPILIONID^ 



oAVTi explanation, Mr. Bates has shown that certain groups of butterflies have a defence 

 against insectivorous animals, independent of sfl-iftness of motion. These are generally 

 very almndant, 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 PapiUo 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 costa and falcate 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 Poli/dorus-grouf (to which belongs the 

 only unchanged Celebesian Fapilio), 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 Danaidse are in the same position : they are slow and 

 weak fliers ; yet they abound in species and individuals, and are the objects of mimiciy. 

 The Satyridae have also probably a means of protection — perhaps their keeping always 

 near the ground and their generally obscure colours ; while the Lycsenidse and Hesperidae 

 may find secm-ity in theii- small size and rapid motions. In the extensive family of the 

 I\ ymphalidse, however, we find that several of the larger species, of comparatively feeble 

 structure, have their wings modified (Cethosla, Llmenitis, 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 grovxps, 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 sui-rounding islands. Increased powers of flight, or rapidity of 

 turning, was advantageous in baifling this enemy ; and the peculiar form of wing necessary 

 to give this would be readily acquired by the action of " natm-al 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 Ely-catchers of Borneo and Java on the one side {Muscipeta, Fhilentoma), and of the 

 Moluccas on the other {Monarclia, Bhipidura), are almost entirely absent from Celebes. 

 Theii- place seems to be supplied by the Caterpillar-catchers {Grcmcalus, Campepliaya), 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*. However this may be, the 

 fauna of Celebes is undoubtedly highly peculiar in every department of which we have 



* Mr. Bates has suggested that the larger Dragon-flies {jSshna, &c.) prey upon butterflies ; but I did not notice that 

 they were more abundant in Celebes than elsewhere. 



