THE CHALK-HILL BLUE 21 



PLATE XI 



THE CHALK-HILL BLUE (1) 



You cannot possibly mistake the male of this 

 butterfly for any other insect, for the upper surface 

 of both its front and hind wings is of the most 

 beautiful silvery greenish-blue colour, shading 

 off into a blackish band along the hind border. 

 In fact, as a great naturalist once said, it always 

 makes one think of a bright moonlight night, 

 while the "Clifton blue" reminds one of the sky 

 on a clear summer's day. But the female is so 

 exactly like that of the " Clifton blue " that it is 

 hardly possible to tell the one from the other. 



This lovely butterfly is hardly ever found except 

 on chalky downs, and is commonest in the south 

 of England. It flies in July and August. If you 

 want to find the caterpillar, you must look for 

 it in May and the early part of June. It feeds 

 upon bird's-foot trefoil and kidney-vetch, and 

 looks rather like a fat little green woodlouse, 

 with six yellow stripes upon its back and sides; 

 and if you look at these stripes closely, you will 

 see that they are really made of rows of tiny 

 yellow spots. About the middle of June it fastens 

 itself to the stem of its food-plant by spinning a 

 silken band round its body, and then turns into 

 a greenish-brown chrysalis. 



