EXPLANATION OF FORM AND COLOURING. 2ll 



in the forest, etc.) have all produced results pointing in the same direction. 

 It is perhaps jet more important, for it is this that best enables us to judge 

 ol: the extent of such persecution as is suffered by butterflies, that I have 

 obtained good direct evidence in favour of the view that it is birds that 

 probably chiefly inflict the wounds that are present sometimes in the wings 

 of nearly every fairly high-grade butterfly one sees. 



2. Discrepancies between the attitude of ivild and tame individuals of the 

 same sjjecies towards the same food. In animals (and especially, amongst 

 birds, in hand-reared nestlings) that have become accustomed to a particular 

 kind of food I have often noticed the growth of a kind of conservatism that 

 makes them reluctant after a time to try new foods, even foods that are 

 eaten freely by other individuals, wild or captive, of the same species — and I 

 shall describe^ when I come to it, a particularly good contrast of this kind 

 that occurred between two of my captive bulbuls. 



I shall also have much to say, even in this introduction, of exactly the 

 opposite phenomenon — namely, the tendency of animals accustomed to a wide 

 range of food to develop special eagerness for food of which they are largely 

 deprived and relative indifference or .even repugnance to the foods they chiefly 

 receive. 



These two principles I have seen illustrated at different times even in a single 

 individual (a lemur, Galago crassicaudatus) and, with that to be described 

 in the next paragraph, they have seemed to me to be largely capable of 

 accounting for, at any rate, such cases of apparent discrepancy as I have myself 

 come across. 



3. Apparent indiscriminateness of ivild birds. My experiments on wild 

 birds (at any rate) show that it does not require, necessarily, literal starvation 

 to make a bird eat DanaiuEe and Acrseinpe : a mere empty stomach (in some 

 birds rather less) — combined with a good hungry appetite — may suffice. When 

 it has eaten a little food it will refuse insects of this very low grade, but 

 accept others which will in turn be refused with growing repletion, though 

 insects that are a little pleasanter will continue to be taken : and so on, 

 through several grades, up to actual repletion-point, near which only the 

 very " pleasantest '" insects of all will be accepted. This is a statement which 

 my experiments will be found to support in the most ample manner, and the 

 fact stated will probably in most cases account for the frequent eating 

 of low-grade insects by wild birds ; for the refusal sometimes by captive birds 

 of food that the species is known to eat in the wild state and vice versa ; and 

 for much that might be regarded as inconsistency on the part of captive 

 animals. ■ I could give many instances of the working of the principle, but 

 the following must suffice : — 



(a) Flocks of ivild bee-eaters (Merops apiaster) mai/ daily be seen eating 

 immense numbers of hive-bees, and 1 have taken as many as 23 from a single 



