THE LARGE CABBAGE WHITE BUTTERFLY 183 



thousands of minute overlapping scales (whence the name Lepi- 

 doptera Butterflies and Moths ; Greek, Igpis = scale), which 

 cover both surfaces. In the male the tip of the front wing has 

 a very narrow black border, which widens out as it reaches the 

 front angle and passes more than half-way along the outer edge, 

 gradually fading out before reaching the hind angle ; in the female 

 the expanded portion of the black colouring is rather more ex- 

 tensive, and there are in addition two large black spots on the 

 surface of the wing, one above the other, and 

 separated by about as much white as their 

 own width, situated rather more than half- 

 way from the shoulder to the outer edge ; 

 below the lower of these spots, and almost 

 touching it, there is also in this sex a club- 

 shaped black streak whose point is directed 

 towards the shoulder. On the hind- wing 

 both sexes have a black spot on the front 

 edge, in a line with the two on the fore-wing 

 of the female ; this spot is larger in the 

 female, and has the appearance of being two 

 spots coalesced. The lower side of the wing 

 is alike in both sexes, the male as well as the 

 female having the two black spots upon the 

 fore-wing, but none of the other black marks, 

 excepting a small part of that on the hind- wing, appear. The 

 general colour of the under side, especially of the hind-wing, is 

 greenish yellow in a fresh specimen. When at rest the insect raises 

 the wings, without any folding or creasing, over its back, so that 

 right and left meet, and only the greenish under side of the hind- 

 wing is visible. The insect is thus to some extent concealed 

 when upon the foliage of plants. The wings are strengthened by 

 veins or nervures, of which the most anterior are the strongest. 

 The precise arrangement of nervures, or wing- venation, is of 

 great importance in the classification of Lepidoptem, and should 

 be examined by all who intend to make a serious study of the 

 group. Details are not easy to see so long as the scales of the 

 wing are in position ; but this difficulty may be overcome by one 

 or other of these methods : (i) brush off the scales with a moist 



FIG. 67. Scales from 

 the wing of a butter- 

 fly. 



