130 Mr. G. A. K. Marsliall on Bia-jjosematism, with reference 



conditions woulil be likely to occur very frequently during 

 the dry winter months in South Africa. Here again I 

 find some confirmatory evidence among my experiments 

 (Trans. Ent. Soc. 1902, p. 344). A tame kestrel {I'innun- 

 cnlus naumanni), which had shown pronounced dislike of 

 both AcraBas and Danaida cJtri/sip2)us, was starved for 

 twenty-four hours. After eating seven palatable butter- 

 flies it was given two Acrceas, which were swallowed 

 whole ; then a I), chriisii'ipns was ottered to it, which was 

 tasted but emphatically rejected, and immediately after- 

 wards three more Aeneas were swallowed whole. Thus 

 under the stress of hunger the bitter juices of the Acroeas 

 were disregarded, but the more highly unpleasant flavour 

 of the Danainc still remained a deterrent. 



From these remarks we see that the interpretation of 

 Batesian mimicry is not to be restricted only to those 

 cases where an edible species mimics an inedible model ; 

 but while in MuUcrian mimicry the essential condition is 

 a difference in the individual numbers of two inedible 

 species, in Batesian mimicry the essential condition is 

 a difference in the palatability. Both species may be 

 distasteful, but wherever there is scope for preference, 

 there it is possible for Bates' principle to operate. Thus, 

 so far from being able to accept the suggestion that 

 practically all mimicry among butterflies is Miillerian in 

 character, it seems to me that we have not yet begun to 

 appreciate how wide a significance Bates' principle may 

 have. The question is extremely complex, and resolves 

 itself ultimately into a consideration of the mental atti- 

 tude of insectivorous animals towards their prey. It is 

 even possible for a single species to be at the same time 

 both a Miillerian and a Batesian mimic of one and the 

 same sjiecies in relation to the attacks of different enemies. 

 The final decision on these points must rest with the 

 field-observer and experimenter. 



On tlic greater 'predominance of the factors ivhich make for 

 Batesian mimicry. 



There are some general considerations which also appear 

 to negative the supposition that the occurrence of Miillerian 

 mimicry is far in excess of Batesian. It has already been 

 argued (p. 113) that the operation of the Miillerian factor 

 is practically restricted to the breeding season of birds, 



