EASTERN UNITED STATES. 



31 



FIG. 7. 



or lower branch of the median 2, the second branch 3, 

 and so on round the outer margin and costa to the costal 

 vein, which will have the highest number. If, however, 

 there are two veins below the median, the subniedian and 

 internal, the first is called 1 a, the second 1 6. The same 

 system is observed with the hind wings. 



The membranes of the wings are concealed beneath a 

 covering of minute colored scales. The membrane itself 

 is not colored, the colors of 

 the wing being due to the 

 various hues of the scales. 

 These are arranged in regular 

 rows (see Fig. 7), and lap 

 over one another like shingles 

 on a roof. The scales are 

 modified hairs, and are of 

 various shapes. The basal end 

 by which the scale is attached 

 to the wing comes more or 

 less abruptly to a point ; but the other end varies, being 

 rounded or variously toothed or pointed. This covering 

 has gained for these insects the scientific name Lepidop- 

 tera, from two Greek words which signify scaly-wings. 



These scales cover both the upper and the lower surface, 

 and they are usually of a different color below from what 

 they are above. Sometimes this difference is merely a 

 difference in shade of the same general color, at other 

 times it is more than that, as in the Papilios, etc. The 

 two sexes are often different on the upper surface, but 

 are more nearly alike beneath, as in many of the Pam- 

 philas. 



The abdomen is either oval, as in Papilio, Vanessa, 



Section of butterfly-wing showing 

 how the scales are attached. 



