BUTTERFLY FLIGHT 



173 



a provident instinct leading them to choose unoccupied plants 

 for their eggs ; and when there are many mothers of the 

 flock, they tend to scatter over a wide area when they 

 are butterflies of naturally vagrant mood. After a cycle of 

 warm dry summers the conspicuously chequered wings of 

 the marbled white are often seen on dry slopes many miles 

 from their usual strongholds. The last time when their 

 migration became marked was about 1900 and 1901 ; then set 

 in a series of predominantly wet, cold summers, unfavourable 

 to all butterfly life, and the marbled whites sank back again 

 to the cradles of their race on 

 the dry chalk and limestone 

 hills. Many butterflies are 

 more brilliant, but none more 

 pleasant to the eye, or racier 

 of their own particular soil, as 

 they hover with chalk-spotted 

 wings on the thymy lip of the 

 white chalk-pits. 



In July the chalk-hill blue 

 comes out to reinforce the 

 common blues, diminished a 

 little since June ; and he too seems to have the chalk soil 

 in his blood, for the blue of his wings is densely filmed with 

 milk-white, like the blue of the palest summer sky. He is 

 larger and stouter than the common blue, and is chiefly 

 found on the same chalk and limestone hills as the marbled 

 white. In him we see once again that characteristic veiling 

 of the clearest early summer tints which so many flowers 

 and insects display after the longest day. With the mauve 

 scabious comes the filmy tinge of the chalk-hill blue; the 

 azure speedwell has passed, and the common blues are 

 growing less numerous and more ragged. The flowers of 



MARBLED WHITE 



