TRUE MIMICRY 97 



by selection. It has been asserted that butterflies are exposed to 

 injury from birds only to an inconsiderable extent, not sufficient to 

 account for such an intense and persistent process of selection, 

 because they are not very welcome morsels, on account of the large 

 and uneatable wings and the relatively small body. Doubt has also 

 been raised as to the immunity of the models, which has not been 

 proved in many of the species in regard to which it is assumed. 

 Finally, it is maintained that the advantage which resemblance to an 

 immune model brings is not proved, but is purely hypothetical; and 

 that it is probable that the birds do not distinguish the colours 

 and markings of the flying butterflies at all, but are at the most 

 only deceived by resemblances in their manner of flight. 



The last objection contains a certain amount of truth, inasmuch 

 as the manner of flight always plays a part in the mimicry of 

 a strange species. We shall see later how much the instincts of 

 a species contribute to the deception in all cases of protective colour- 

 ing. It is, therefore, not improbable that, in many cases, the imita- 

 tion of the flight of an immune species, and a gradually increasing 

 familiarity with the habitats of the same immune species, preceded the 

 modification of the colour. Indeed, the slow flight of immune species 

 (Heliconiidse) has been unanimously emphasized by observers, as 

 a factor in facilitating the recognition of the butterflies by the sharp- 

 sighted birds. 



That it was not only in earlier ages of the world's history that 

 butterflies were much persecuted, as some have supposed, but that 

 they are so still, seems to me indisputable in view of the observations 

 of the last quarter of a century. Even in this country, where both 

 butterflies and insect-eating birds are being more and more crowded 

 out through cultivation, a considerable number of butterflies in flight 

 fall victims to the birds. Kennel gives observations on this point 

 in regard to the white-throat; Caspari for the swallows. The latter 

 let about a hundred little tortoiseshell butterflies (Vanessa antiopa) 

 fly from his window, ' but not ten of them reached the neighbouring 

 wood,' all the rest being eaten by swallows, 'which congregated in 

 numbers in front of his window.' Kathariner observed, in the 

 highlands of Asia Minor, a flock of bee-eaters (Merops) which caught 

 in flight and swallowed a great many individuals of a very beautiful 

 diurnal butterfly (Thais eerisyi). 



Finally, Pastor Slevogt has collected much evidence to show that 

 our indigenous butterflies have a great deal to suffer in the way 

 of persecution from birds. And in regard to tropical countries, the 

 chase of butterflies by insectivorous birds has long been known. 



