40 CONTROLLED NATURAL SELECTION 
it may be induced to strike them rather than 
more vulnerable parts, which have not eye- 
spots. Other marks and colourings serve 
the same purpose ; for instance, the brilliant 
under-wings of many moths. 
Here are examples of purposely conspicuous 
characters whose function is to attract enemies. 
Whenever conspicuous colouring is found on 
invulnerable parts, the question must be asked, 
Is this an attracting mark? There is some 
evidence that these marks are by no means 
uncommon. In birds, for instance, the con- 
spicuous marks and bars on wings and tail 
may be of this nature. As is often the case in 
insects, they are concealed when at rest and 
displayed during flight, and may cause enemies 
to strike at tail or wing and thus not injure 
vital parts. 
It is noteworthy that although young as 
a rule do not present conspicuous colouring, 
they do usually have these attraction marks. 
(For examples see Chapter IX.) 
It will be well to review the conclusions 
which have been arrived at in the last two 
chapters : 
1. Purposeful conspicuousness of animals 
is a fact of Nature. 
2. It is produced in animals by means of 
