SOIL BUILDERS 13 



addition of vegetable matter from decaying plants ; 

 yet, when we reflect upon it, the excrements and 

 the remains of all creatures upon the earth must 

 aggregate a considerable amount. 



Of no small importance also, are the burrows, 

 channels, holes, etc., in which animals live or by 

 which they feed. Ants, moles, gophers, wood- 

 chucks, and the like are insignificant soil builders 

 as individuals, but in the aggregate they have 

 great influence. Ants are abundant on many of 

 the lighter soils and often exercise a profound in- 

 fluence on their structure and agricultural value. 

 Shaler has calculated that ants bring to the surface 

 of a four-acre field, in Cambridge, Massachusetts, 

 enough sand and fine soil to cover the entire area 

 one-fifth inch deep each year. This is probably a 

 larger amount of material than ants move in most 

 places, although those of us who have had to fight 

 ants in lawns are quite willing to accept these 

 figures; but they call our attention to the insidious 

 and far-reaching influence that these tiny creatures 

 may exert. Since the material brought to the 

 surface by the smaller ants is mostly fine sand and 

 smaller particles of soil, they being unable to move 

 the larger particles, it is evident that the texture of 

 the surface soil must be greatly modified by their 

 industry. 



The mounds built by the large black and brown 

 hill-building ants are often two feet in height and 

 four feet in diameter. They are composed mostly 

 of soil brought from below, mixed with bits of 

 leaves and bark. They are being washed down 

 constantly by rains and added to the surface soil. 

 These ants usually build a new mound each year. 

 Furthermore, the subterranean burrows and chan- 

 nels of ants, penetrating as they do from several 



