STUDY OF BUTTERFLIES ALONE 229 



4. Mimetic Resemblance and Common Warning Colours 

 between different Arthropod Classes and between various 

 Insect Orders, and their Relation to Similar Resemblances 

 within the Limits of a Single Order. 



The various criticisms of Natural Selection as the 

 motive cause of Mimicry have been based almost ex- 

 clusively upon the phenomena presented by Mimetic 

 Resemblance and Common Warning Colours among the 

 species of a single Order of insects (Lepidoptera), and 

 generally the species of one Family (Nymphalidae), and 

 one Sub-Family (Pierinae). I cannot but think that this 

 limitation of the survey to one small part of the field over 

 which the resemblances commonly occur is, in large part, 

 the cause of the rejection of Natural Selection and the 

 substitution of alternative suggestions. There is some- 

 thing attractive and plausible in the idea that the strong 

 mutual resemblances within a group of butterflies of 

 different genera and Sub-Families, inhabiting a single 

 locality, are due to the direct action of peculiar local 

 physical or chemical influences; but the suggestion loses 

 all its attractiveness when it is applied to the resemblance 

 between a spider and an ant, or a moth and a wasp. 

 And yet few could bring themselves to believe that the 

 resemblances which are here contrasted have been built 

 up by two entirely different sets of forces. — 



The majority of naturalists will probably agree with 

 this argument, and, realizing that the theories of External 

 Causes and of Internal Causes are useless to explain the 

 mimetic likeness between a wasp and an insect of a 

 different Order, will reject these theories as unnecessary 

 to explain the resemblance between one butterfly and 

 another. But an attempt may be made, in fact has 

 been made, to discriminate between the relative powers 

 of the Batesian and Miillerian Theories 'respectively in 

 these two spheres of Mimetic Resemblance — that which 

 includes forms of remote affinity and that which includes 

 those more nearly akin. It has been supposed that the 

 Mullerian Theory does not explain Mimetic Resemblances 

 between remote forms, however adequate it may be for 



