Mimetic Attraction. 323 



tlie expense of other individuals of the same species, some 

 of which must necessarily fall victims to their insectivorous 

 enemies during the " education " of the latter as to the 

 kinds of prey to be sought or avoided. Each form that 

 thus succeeds in establishing itself becomes, in propor- 

 tion to its nauseous character and the ease with which it 

 can be recognised, a centre of attraction for other species, 

 which, by assimilating their own aspect to that of their 

 model, ai-e enabled to share in the immunity from attack 

 enjoyed by the latter. It is now considered probable by 

 many that this power of attraction is exercised by 

 dominant inedible species over edible and inedible forms 

 alike ; there is, however, one important difference be- 

 tween the two cases, which I have before endeavoured to 

 point out, but which seems to need a more explicit state- 

 ment than has yet been given to it. 



Let us first take the case of a species which is edible, 

 and therefoi'e liable to extermination by insectivorous 

 animals. The chances of the survival of such a species 

 depend on the excellence of its means of defence ; such as 

 superior swiftness, or the power of concealment, whether 

 by resemblance to inanimate objects, or to some other 

 species protected by a disagreeable flavour. The force 

 which impels an edible species to seek protection by the 

 last-named method, viz., by sheltering itself under the 

 reputation of a conspicuous inedible form, is the well- 

 known " Batesian mimicry. '' With reference to this, 

 which is the most complete kind of mimiciy, it is to be 

 observed that the advantage of association is all on the 

 side of the mimic, and is not shared in the least degree by 

 the model. Indeed, the existence of the edible mimicking 

 species is a source of danger to the form mimicked, 

 inasmuch as any experience gained by tasting the former 

 would be used to the detriment of the latter. From these 

 considerations two consequences follow ; the first being 

 that such an association can subsist only when the 

 numbers of the mimic are insignificant compared with 

 those of the model, for otherwise the latter^s reputation 

 for inedibility would be interfered with, and eventually 

 destroyed. The second consequence is that the attrac- 

 tive force leading to assimilation between the two forms 

 can act only in one direction ; i.e., the model attracts the 

 mimic, but the mimic can exert no reciprocal influence 

 upon the model. The latter stands secure upon its own 



