238 FORMATION AND GROWTH OF 



they resort their yearly work is much more conspi- 

 cuous than the annual worm-work. In Leicester- 

 shire, for instance, and elsewhere in central En^- 



/ ' O 



land, the hill-building ants are a nuisance to the 

 grazier. In the spring the ants may be observed 

 beginning their work, and from that time they 

 carry on their operations all through the summer, 

 to the late autumn or early winter. On a moor 

 they raise hillocks scattered about over the ground,- 

 getting closer and closer together as the colonies 

 increase. But where the ants are most useful is in 

 places where crags and large stones are mixed up 

 with patches of sandy peat. In such a locality they 

 will always build on a rock, the foundation of their 

 habitation being at its junction with the soil. These 

 ants seldom raise their structures as high as the 

 moorland ants do, but they make up in extent, for 

 deficiency in height; and by this means the rocks 

 are gradually covered with soil and vegetation ; for, 

 on account of the season of the year at which they 

 build, the growth of the plants keeps pace with the 

 formation of the ant-soil, and protects it in a great 

 measure from meteoric abrasion. During the winter, 

 however, the shape of the ant-hills is' somewhat 

 modified ; but the matted roots of the plants preserve 

 the major part of the soil, which will thus remain, 

 forming an envelope for the rock. 



As the annual work of one colony is rarely less 



