INTRODUCTION. 57 



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 insertion of the scales. The latter are so mi- 

 nute that they appear to the naked eye like powder 

 or dust, and as they are very closely placed, their 

 numbers on a single insect are astonishingly great. 

 Leeuwenhoek 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 butter- 

 flies, 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), sometimes measure nearly a 

 foot across the wings ! A modern mosaic picture 

 may contain 870 tesserulse, or separate pieces, in 

 one square inch of surface; but the same extent of a 

 butterfly's wing sometimes consists of no fewer than 

 100,736 ! 



In common with several other extensive races of 

 insects, butterflies derive their nourishment entirely 

 from liquid substances, and the structure of the 

 mouth is consequently very different from that of the 

 masticating kinds. They are hence classed among 

 the haustellated or suctorial tribes of insects. The 

 most conspicuous and elaborately constructed organ> 

 is the long flexible tube projecting from the mouth, 



