The Attacks of Birds upon Butterflies

MR. EVERSHED'S letter in NATURE of August 29 seems to me very suggestive, and it is to be hoped that his hypothesis may be tested by careful observation in many parts of the world. As regards the rarity with which these attacks have been witnessed in India by Mr. Evershed and many other naturalists, it is well to bear in mind the probability that the proportion of butterfly-eating birds differs in the different tropical regions. Indeed, it is difficult on any other hypothesis to understand why butterfly mimicry should be developed to such very different degrees in the three richest regions, being transcendent in the Neotropical, remarkable in the Ethiopian, but relatively poor in the Oriental region. Indirect evidence of the frequency of attacks in different areas might perhaps be obtained by a study of the relative amount of damage which could only have been inflicted by the beak of a bird.