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some cases, many species, and not fall solely upon one. 
They are also mimicked by Butterflies belonging to many 
groups which are not protected, and by some Moths. 
The question of colour generally in Butterflies is an 
attractive one, and one which has led to some interesting 
speculations. The colours of Butterflies are produced partly 
by the pigment deposited in the scales with which the wings 
are covered and partly by what is called interference of light, 
i.e.. the rays are broken up either by refraction from finely 
striated surfaces, or by transmission through one or more 
layers of colourless cells with which the wings are covered. 
In this way are produced the brilliant colours of our English 
Purple Emperior, and those of the glorious Morphos of South 
America. Now what is the object of these wonderful colours 
and markings. Various utilitarian causes have been given. 
As a rule, it is the upper surface which is gaily coloured. 
The colouring of the under surface is generally protective. 
It has been supposed that the brilliant upper surface, which 
is displayed when the insect is on the wing, is for the purpose 
of attracting the opposite sex, and so assisting in the continu- 
ance of the species ; but it must be remembered that owing 
to the fixity of their eyes and their position, Butterflies 
cannot see themselves, neither have they anv power, as in 
the case of birds and mammals, of transmitting their know- 
ledge to their descendants, and the parent Butterflies die 
long before their eggs are hatched. 
It would seem that the sexes in Butterflies and Moths 
are mainly attracted to each other by means of scent, and 
for this purpose in many species the wings are furnished 
with scent-glands in the shape of peculiarly constructed 
hairs. Every Butterfly collector is well aware of the fact 
that if he has a virgin female of certain species, e.g., the 
Oak-egger Moth, in a pill box in his pocket and goes into 
a district where this Moth exists, he will be visited by many 
males, who must be attracted by the scent and not by sight. 
