Birds ill Relation to their Prey. 63 



Comment. It is evident that, starting hungry enough' 

 these birds can go on eating the most nauseous butterflies 

 indefinitelj and with apparent relish, provided intervals 

 without pleasauter food are interspersed to keep them hungry 

 enough, or to bring them back to that point when they have, 

 by eating several, been brought up against the safety-limit. 

 Not that in the case of these particular birds the hunger that 

 will enable them to digest such insects need be great ! 



529. March 4. — Plalf an hour before the experiment I fed 

 each bird on larval migratory locusts till it refused to eat 

 more. The idea was to pit Amauris against large Acrajas, 

 and to see oE which most would be eaten, and the locust-food 

 was to equalize the start. A to be given the Acrteas, B the 

 others. 



A ate readily 12 u.lcnca natalica with a 15-minutes' interval 

 after the 7th, and two more with hesitation ; an Amauris 

 atbimaculata readily, and, again after hesitation, a fifteenth 

 Acrcea natalica. 



B ate 4 Amauris loben<jula,iiud a fifth after hesitation, and 

 repeatedly refused a sixth without tasting, and with signs of 

 annoyance. But she greedily ate an Acrcea acara, though 

 she again repeatedly refused A. lohengula with what appeared 

 to be marked dislike. 



Fifteen minutes later A again ate 7 A. natalica^ but with 

 hesitation at the sixth and seventh. He repeatedly refused, 

 without tasting it, an eighth. 



B however refused absolutely to touch even one A.lohengula, 

 though I reofEered it repeatedly. But she greedily ate an 

 Acraa esehria (a small black-and-white species) and an 

 Acraa acara, but again repeatedly refused A. lohengida. 



Thereupon, to test whether she would be deceived by 

 resemblances in her prey, I offered her a mimic of A. lohen- 

 gula — namely, Acrcea johnstoni form confusa, with the upper, 

 mimetic, surface shown. The Hornbill at first ignored it 

 absolutely, as she had done its model, but, on my continuing 

 to hold it to her, she at last began to examine it closely 

 and cautiously, and then, taking it in the point of her 

 bill held it there for some time, turning it over and over 



