248 



THEORIES Ol' MIMICRY 



an explanation on the theory of Natural Selection. Why 

 should examples of Miniicr}- and Common \\\arning 

 Colours be so much more abundant and perfect in one 

 country than another ? The physico-chemical influences, 

 the effects of luxuriant vegetation, as Wallace has pointed 

 out, are very similar in tropical South America, i\Ialaya, 

 and West Africa, and yet the first-named country is 

 pre-eminent in affording examples of the resemblances 

 under consideration. This is not only true of likenesses 

 within the Order of Lepidoptera, it appears to be equally- 

 true within the Coleoptera ; it is true of the reseml)lances 

 oi moths to wasps. It is even more marked in Miillerian 

 Resemblance between protected forms than in the 

 examples of Batesian Mimicry. If the direct action of 

 forces connected with localit)' cannot explain the immense 

 predominance of tropical South America in this respect, 

 we are driven to incjuire whether insect life is especiall)- 

 luxuriant and remarkable in this part of the world, and 

 whether it is not probable that the struggle for existence 

 is especially keen. There is no doubt about the answer 

 to these questions: the variety, peculiarity, and abundance 

 of insect life is far greater than in any other part of the 

 world, and it is a fair inference that the conditions are 

 in an equally marked degree favourable for rapid and 

 complete modifications under the operation of Natural 

 Selection. 



We have not as yet sufficient evidence that mimetic 

 groups and groups with a Common Warning coloration 

 appear at the same time of the year. Such evidence as 

 we have points in this direction. The rarity of the 

 mimetic species is usually stated to be due to their being 

 lost in the swarms of the abundant model. There are, 

 however, a larcre number of cases in which the forms have 

 been caught toeether bv a collector who has passed a 

 limited time in a given locality. 



I am bringing together in the Hope Department of 

 the Oxford University Museum as many examples as 

 possible of mimetic species, captured upon the same day 

 and in the same place as their models. This series, which 

 is kept separate, even now affords very valuable evidence 



