\D\l-ll 203 



much f>r that kind <>f mimi< ry hut how i^ lli.: following Idl 

 \plained .' The Itlmmiiii.-e <>f ihr Ama/mi valley have the 

 form and coloral inn afl the Ih-li. <>niin;e, but the Itimmiin 



arc already highly protected. 'I'hc answer i- that tin's resembl 

 advantage t<> hoth groups, aa it minimi/e^ tli< ir de traction b 



thcM- having In learn hut 01 ; warning >i^n;d> in 



This is the essence of Miilier's famous explanation, which will presently 



itrd with nmrc precision. There are two kinds <>l" nn'iui. 

 the kind described hy Halo, in which an edihi btainfl 



SvTim'ty hy counterfeiting the a|>j)carance of an inedihle species; 2) that 

 observed hy Bates and interpreted hy Miiller, in which both sp 

 inedihle. 'I'liesc' two kinds are known respectively as Batesian and 

 Miillerian mimicry, though some writers prefer to limit the term mimi- 

 cry to tin- Hatesian type. 



Wallace's Rules. The chief conditions under which mimicry o< . 

 have- heen stated hy Wallace as follows: 



kt i. That the imitative species occur in the same areaand occupy 

 the very >ame station as the imitated. 



That the imitators are always the more defenceless. 



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." 



These rules relate chiefly to the Batesian form of mimicry and need 

 to he altered to apply to the Miillerian kind. 



The first criterion given by Wallace is evidently an essential one and 

 istained by the facts. It is also true that mimic and model occur 

 usually at the same time of year; Marshall found many new instances 

 of this in South Africa. In some cases of mimicry, strange to say, the 

 r model is unknown. Thus some Nymphalidae diverge from their 

 relative- to mimic the Euplceinae, though no particular model has been 

 found. In such instances, as Scudder suggests, tfie prototype may exist 

 without having been found; may have become extinct; or the sp< 

 may have arrived at a general resemblance to another group without 

 having as yet acquired a likeness to any particular species of the group, 

 the general likeness meanwhile being profitable. 



The second condition- named by Wallace is correct for fiatesian 

 but not for Miillerian mimicry. 



The fulfilment of the third condition is requisite for the succ- 



