242 
DARWINISM 
CHAP. 
were far less common, so tliat 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. 
How Mimicry lias been Produced. 
The fact has been now established that the Heliconidte 
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 colours—although 
very varied, ranging from deep blue-black, with 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 suffer 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 sufficient 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 persecuted groups have 
not availed themselves of this simple means of protection. 
From the great abundance of the Heliconidse 1 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 
1 These butterflies are now divided into two sub-families, one of which is 
placed with the Danaidae ; but to avoid confusion I shall always speak of the 
American genera under the old term Heliconidse. 
