BUTTERFLY ANB OTHER 8GALT-WINQBD INSECTS. 119 



Fig. 139, which represents a cross-view of that of the Da- 

 nais butterfly. The maxillae in some moths, such as the 

 great, green, tailed Luna moth, are short and separate, like 

 a pair of blades. Now the tongue of the butterfly is formed 

 by the union of these two blade-like maxillae; and they are 

 so closely united together as to form a hollow tube (c), 

 through which the nectar is sucked, so that it passes into 



Fig. 130.— Fore and hind wii^ of a butterfly, showing the venation, o, costal 

 vein; 6, subcostal; 6*. Ifl, o^, 6*, b^, tlie five subcostal veinlets; c, the inde. 

 pendent vein (it is sometimes a branch of the subcostal and sometimes of the 

 median vein); d, median vein; d', d', d', d*, the four median veinlets; e, sub- 

 median vein; /, internal vein; ft, interno-median veinlet. rarely found; band 

 d are situated in the " discal cell." Lettering the same in both wings. 



the mouth. Each side of the tongue contains a nerre, 

 muscles and an -air- tube {tr). 



The wings of butterflies are beautifully painted and or- 

 namented. If, howerer, we examine the scales separately 

 under the microscope, we shall see that they are colorless. 

 The variety of color on the different spots and bands is 

 due to the arrangement of the scales, i.e., to the interfer- 

 ence of the rays of light passing through them. 



