Many objections have been made to the interpretation of mimicry 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 colouring. It is, therefore, not improbable that, in many cases, the imitation 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 (Heliconiidæ) 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 cerisyi_).