PROTECTIVE MIMICRY 231 



all mimetic resemblances are due to natural selection 

 contrasts in the strongest manner with the entire 

 absence of any alternative theory on the part of Mr. 

 Bates's critics. 



Conditions under which Protective Mimicry occurs 



The conditions under which Mimicry occurs also 

 strongly confirm the view that these resemblances 

 have been produced by the operation of natural selec- 

 tion. These conditions have been found to be very 

 nearly constant by every naturalist who has published 

 any observations on the subject. They have recently 

 been very concisely stated by Mr. Wallace as fol- 

 lows.^ 



* 1. That the imitative species occur in the same 

 area and occupy the same station as the imitated. 



* 2. That the imitators are always the more de- 

 fenceless. 



' 3. That the imitators are always less numerous 

 in individuals. 



' 4. That the imitators differ from the bulk of 

 their allies. 



' 5. That the imitation, however minute, is external 

 and visible only, never extending to internal characters 

 or to such as do not affect the external appearance.' 



» Darwinism, pp. 264. 265. 



