160 SOILS. 



Insects of various kinds are also instrumental in producing, 

 not only the uniform distribution of humus in the surface soil, 

 but also the looseness of texture which we see in forest soils 

 especially. Ants, wasps, many kinds of beetles, crickets, and 

 particularly the larvae of these, and of other burrowing crea- 

 tures, often form considerable accumulations, due directly both 

 to their mechanical activity, and to their excrements. 



The work of ants is in some regions on so large a scale as to 

 attract the attention of the most casual observer. Especially 

 is this the case in portions of the arid region, from Texas to 

 Montana, where at times large areas are so thickly studded with 

 hills from three to twelve feet in diameter, and one to two feet 

 high, that it is difficult to pass without being ^attacked by the 

 insects. The " mounds " studding a large portion of the 

 prairie country of Louisiana seem also to be clue to the work 

 of ants, although not inhabited at present. 



Larger burrowing animals also assist in the task of mixing 

 uniformly the surface soils, and aiding root-penetration, as well 

 as, in many cases, the conservation of moisture. Seton (loc. 

 cit.) even claims that the pocket gophers (Thomomys) in a 

 great degree replace the activity of the earthworms in the arid 

 region, where they, together with the voles (commonly known 

 there as field mice), exist in great numbers. Of course the 

 work of these animals, as well as that of the prairie dogs, 

 ground squirrels, badgers, etc., is incompatible with cultiva- 

 tion. But the effects of their burrows on the native vegeta- 

 tion, and the indications they give of the nature of the subsoil, 

 are eminently useful to the land-seeker. 



Thus in the rolling sediment-lands of the Great Bend of the Columbia, 

 the observer is surprised to see the " giant rye grass," usually at home 

 in the moist lowlands, growing preferably on the crests of the ridges 

 bordering the horizon. Examination shows that this is due to the 

 burrowing of badgers, whereby the roots of the grass are enabled to 

 reach moisture at all times, even in that extremely arid region. 



