INTRODUCTION. xli 



be described in a separate section. The wing-membrane 

 itself is colourless and transparent, but is clothed with fine 

 scales, which are easily rubbed off, if the insect is handled 

 roughly. 



"The mode of painting employed to produce these rich tints 

 may not improperly be called a kind of natural mosaic, for the 

 colours invariably reside in the scales, which form a dense 

 covering over the whole surface. These scales are usually of 

 an oval or elongated form, and truncated at the tip, where they 

 are occasionally divided into teeth ; but sometimes they are 

 conical, linear, or triangular. A considerable number of the 

 forms which they exhibit are represented at the top of Plate I. 

 Fig. 2 shows the form which they sometimes assume in the 

 fringe which surrounds the wing. They are fixed in the wing 

 by means of a narrow pedicel, and are most commonly dis- 

 posed in transverse rows, placed close together, and overlapping 

 each other like the tiles of a roof. In some instances they are 

 placed without any regular order, and in certain cases there 

 appear to be two layers of scales on both sides of the wings. 

 When they are rubbed off, the wing is found to consist of an 

 elastic membrane, thin and transparent, and marked with 

 slightly indented lines, forming a kind of groove for the in- 

 sertion of the scales. The latter are so minute that they 

 appear to the naked eye like particles of dust, and as they are 

 closely placed, their numbers in a single insect are astonishingly 

 great. Leesewentock counted upwards of 400,000 on the wings 

 of the Silk-Moth, an insect not above one-fourth of the size of 

 some of our native Butterflies. But how much inferior must 

 this number be to that necessary to form a covering to some 

 foreign Butterflies, the wings of which expand upwards of half 

 a foot ; or certain species of Moths, some of which, such as the 

 Atlas-Moth of the East, or the Great Owl-Moth of Brazil, some- 

 times measure nearly a foot across the wings ? A modern mo- 



