r>i8 



THE MECHANICAL FUNCTIONS. 



the wing where the scales have been rubbed off, 

 are shown in Fig. 165, which is a faithful delinea- 

 tion of the appearance of the wing of the Hesperia 



Sloani, seen through a powerful microscope. The 

 membrane of the wing itself, when stripped of its 

 scales, is as perfectly transparent as that of the bee, 

 and is, in like manner, supported by diverging 

 nervures. Many butterflies exhibit, in some parts 

 of the wing, smooth pearly spots, called by ento- 

 mologists, ocelli, or eyes, which arise from those 

 parts being naturally destitute of scales. The num- 

 ber of these scales necessary to cover the surface 

 of the wings must, from their minuteness, be 

 exceedingly great. The moth of the silk worm 

 {Bomhyx 7nori, Fig. 148), which has but a small 

 wing, contains, according to Lewenhoeck, more 

 than two hundred thousand of these scales in each 



wing 



* 



* The account of an elaborate examination of the scales of the 

 Lepidoptera, by Bernard Deschamps, is given in the Ann. Sc. Nat. 



sene 



ni. 



111. 



