242 DARWINISM chap. 



were far less common, so that Mr. Bates estimated the pro- 

 portion in some cases as not one to a thousand. Before 

 giving an account of the numerous remarkable cases of mimicry 

 in other parts of the world, and between various groups 

 of insects and of higher animals, it will be well to explain 

 briefly the use and purport of the phenomenon, and also the 

 mode by which it has been brought about. 



Hoio Mimicry has leen Produced. 



The fact has been now established that the Heliconidse 

 possess an offensive odour and taste, which lead to their 

 being almost entirely free from attack by insectivorous 

 creatures ; they possess a peculiar form and mode of flight, 

 and do not seek concealment ; while their coloiu-s — although 

 very varied, ranging from deep blue-black, Avith white, yellow, 

 or vivid red bands and spots, to the most delicate semitrans- 

 parent wings adorned with pale brown or yellow markings — 

 are yet always very distinctive, and unlike those of all the 

 other families of butterflies in the same country. It is, 

 therefore, clear that if any other butterflies in the same 

 region, which are eatable and suff"er great persecution from 

 insectivorous animals, should come to resemble any of these 

 uneatable species so closely as to be mistaken for them by 

 their enemies, they will obtain thereby immunity from per- 

 secution. This is the obvious and sufiicient reason why the 

 imitation is useful, and therefore why it occurs in nature. We 

 have now to explain how it has probably been brought about, 

 and also why a still larger number of pei'secuted groups have 

 not availed themselves of this simple means of protection. 



Fi'om the great abundance of the Heliconida?^ all over 

 tropical America, the vast number of their genera and species, 

 and their marked distinctions from all other butterflies, it 

 follows that they constitute a group of high antiquity, which 

 in the course of ages has become more and more specialised, 

 and owing to its peculiar advantages has now become a 

 dominant and aggressive race. But when they first arose 

 from some ancestral species or group which, owing to the food 



' These Imtterflies are now divideil into two sub-families, one of wbicli is 

 placed with the Daiiaid;e ; but to avoid confusion I shall always speak of the 

 American genera under the old term Helicouidae. 



