118 THE ENEMIES OF BUTTERFLIES [ch. 



devoured. When first offered this unpalatable species 

 was taken readily and it was only after it had been 

 tasted that the bird rejected it. When offered on 

 several subsequent occasions it was partly eaten each 

 time, and the behaviour of the Kestrel did not suggest 

 that it associated a disagreeable flavour even with this 

 conspicuous pattern. Another young Kestrel (Cerch- 

 neis rupicoloides) was also used for experiment. At 

 first it would not take butterflies and at no time did 

 it shew any fondness for them. Indeed it is doubtful 

 from the way in which they seem to have shaped at 

 the insects whether either of these Kestrels had had any 

 experience of butterflies before the experiments began. 



A Ground Hornbill with which Marshall also ex- 

 perimented ate various species, including Acraea, but, 

 after crushing it, refused the only Danais chrysippus 

 offered. It is hardly likely that this large omnivorous 

 bird operates as a selecting agent in cases of mimicry. 



In an interesting paper published recently McAfee 1 

 discusses the value of feeding experiments with animals 

 in captivity as a means of indicating their preference 

 for different articles of diet. After reviewing the 

 various evidence brought forward he concludes that 

 the food accepted or rejected by captive animals is 

 very little guide to its preferences under natural con- 

 ditions. He points out that a bird in captivity not 

 infrequently rejects what is known to form a main 

 staple of its diet in nature, and that conversely it may 

 eagerly accept something which, in the wild state, it 



1 Proc. Acad. Nat. Sci. Philadelphia, 1912. 



