DISINTEGRATING WORK OF ANIMALS. 449 



from 10 to 30 feet [3 to 9 meters] across at the base. The new ones are 

 steeply conical and the old ones are rounded or flattened down by the 

 weather. In many places these mounds are so close together that then- 

 bases touch each other. About the Urucu station the ant-hills are so thick 

 that the country looks like a field of gigantic potato hills."" 



The termite nests, above the average surface, are said by Branner to 

 be from one-third to 3J meters in height, and from one-third to 3 meters in 

 diameter. He further says that along the upper Paraguay he has seen 

 "places where the nests are so close together that one could almost walk 

 upon them for several hundred yards [one-half a kilometer] at a time, while 

 over many acres of ground no one of the nests was more than 10 feet 

 [3 meters] from another." b Brainier further states that innumerable anas- 

 tomosing galleries are made underground from a depth up to 3 meters or 

 more. " The underground galleries of the saubas penetrate the soil to 

 great distances. These ants are very injurious to vegetation, and one of 

 the methods used by the planters to kill them is to blow poisonous fumes 

 into their burrows. I have seen these fumes, blown into one of these 

 openings, issue several hundred, even 1,000, feet [312 meters] away." c 



Even in the temperate regions in favorable locations the number of 

 ant-hills on an acre is very great, and each hill may A^ary from one to 

 several feet in diameter, and from a few centimeters to a meter in height. 

 Shaler calculates that the ants in a certain field in Massachusetts transfer 

 annually half a centimeter of material from the subsoil to the surface. He 

 explains the freedom from pebbles of certain sandy soils of New England 

 resting upon a subsoil containing pebbles as due to the upward transporta- 

 tion of the soil by the ants in making their mounds/ 



Besides ants and termites there are many other small burrowing 

 animals, such as beetles and wasps, but these are comparatively unim- 

 portant. 



The larger burrowing animals. — The larger burrowing animals are very numer- 

 ous. Of these some of the more important are the prairie dog, rabbit, 

 mole, badger, woodchuck, gopher, and ground squirrel. In many regions 



a Branner, J. C, Ants as geologic agents in the Tropics, cit., p. 151. 



6 Branner, J. O., Decomposition of rocks in Brazil, cit., p. 299. 



e Branner, J. C., Decomposition of rocks in Brazil, cit., p. 296. 



''Shaler, N. S., The origin and nature of soils: Twelfth Ann. Rept. U. S. Geol. Survey, pt. 1, 

 1891, p. 280. Merrill, George P., Bocks, rock-weathering, and soils, Macmillan Co., New York, 1897, 

 pp. 389-390. 



MON XLVII — 04 29 



