178 Grey Rock and Thyme 



trees and shrubs, and a multitude of obscurer 

 herbs and grasses. The boundaries of the moths' 

 and butterflies' haunts are scarcely less sharply 

 denned. There is one abundant but local moth, 

 the treble-bars, of which the slender caterpillar 

 feeds on the leaves and blossoms of the perforated 

 St. John's wort. It is therefore confined to the 

 dry or stony localities where this plant is found ; 

 and the margins of thickets on the limestone are 

 one favourite haunt. 



Throughout a large part of the summer the grey 

 wings of the treble-bars may be seen dashing up in 

 precipitate zigzag flight at almost every step from 

 the broken, stony ground ; the moths are more 

 abundant even than the grasshoppers, which love 

 these hot, dry slopes. But wildly as the grey moth 

 seems to hurl itself upon the air, it is seldom found 

 even a single field away from the margin of its 

 proper soil. Sometimes, in windy weather, a single 

 waif may be disturbed from a more distant hedgerow 

 on the clay ; but it is as impossible for it to rear its 

 kind in this barren spot, void of the least sprig of its 

 indispensable herb, as for an Arab to colonize the 

 snows. 



In their bolder and more broken tracts the hills 

 of mountain limestone provide some of the most 

 individual features of English scenery. The bare 

 protrusions of rock, which are characteristic of the 

 hillside pastures, even when they are hardly large 

 enough for two sheep together to couch on their 

 well-drained warmth, become, on a larger scale, 

 the great scars and terraced crags of some of the 



