PEOOFS OF OKGA.XISIXG Ail.XD 327 



scales, whose chief or only function aijpears tu be tu paint 

 them with all the colours and all tlie glittering reflections of 

 the animal, the vegetable, and the mineral kingdoms, to an 

 equal if not a greater extent than in the case of the birds them- 

 selves. The butterflies, or diurnal Le])idoi)tera alone, not only 

 present us with a range of colour and pattern and of metallic 

 brilliancy fully equal (probably superior), to that of l)irds, 

 but they possess also in a few cases and in distinct families, 

 changeable opalescent hues, in which a pure crimson, or blue, 

 or yellow pigment, as the incidence of light varies, changes 

 into an intense luminous opalescence, sometimes resembling a 

 brilliant phosphorescence more than any metallic or mineral 

 lustre, as described in the next chapter. 



And what renders the wealth of coloration thus produced 

 the more remarkable is, that, unlike the feathers of birds, tlic 

 special organs upon which these colours and patterns are dis- 

 played are not functionally essential to the insect's existence. 

 They have all the appearance of an added superstructure to 

 the wing, because in this way a greater and more brilliant 

 display of colour could be produced than even upon the ex- 

 quisite plumage of birds. It is true that in some cases, these 

 scales have been modified into scent-a'lands in the males of 

 some butterflies, and perhaps in the females of some moths, 

 but otherwise they are the vehicles of colour alone; and though 

 the diversity of tint and pattern is undoubtedly useful in a 

 variety of ways to the insects themselves, yet it is so almost 

 wholly in relation to higher animals and not to their own kind, 

 as I have already explained in Cluipter IX. It is generally 

 admitted that insects with compound eyes possess imperfect 

 vision, and their actions seem to show that they take little 

 notice of distant objects, except of lights at night, and only 

 perceive distinctly what is a few inches or a few feet from 

 them; while there is no proof tliat they recognise what we term 

 colour unless as a greater or less amount of light. 



But as regards the effect of the shading and coloration of 

 insects upon the higher animals, who are ahuo^t always their 



