332 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



It is to be noted that the amount of work done in both instances is 

 rather exceptional — that is, localities were selected favorable for 

 exhibiting the activities of worms in one case and of ants in the other. 



I have no trustworthy data showing the amount of earth brought to 

 the surface by termites over a definite area. The places seen where 

 the nests were most abundant were in low, inaccessible grounds on the 

 upper Paraguay. My impression is that in those particular localities 

 there was less earth brought up than in the case of the true ants 

 cited above. 



The sizes of individual white ants' nests were frequently measured. 

 One of the largest I ever saw in Minas Geraes was 6 meters high and 8 

 meters in circumference 2 meters above the ground, and contained 

 30.55 cubic meters of earth, no account being taken of the porous 

 nature of the structure, which would probably reduce this total by 

 3 or 4 cubic meters. 



Another unusually large mound in the State of Minas was 4 meters 

 high and 7 meters in circumference 2 meters above the base, and con- 

 tained 15.59 cubic meters of earth. These are individual cases, 

 however, and I am unable to say how large an area the contents can 

 properly be distributed over, how long the termites were in doing the 

 work, or how large the colonies were that made them. 



In the case of the white ants, the earth undergoes some process of 

 digestion and passes through the bodies of these insects, so that the 

 chemical effect is probably more important than the mere upturning 

 it gets from the true ants. 



ORGANIC MATTER. 



The true ants carry into their burrows enormous quantities of leaves 

 and other organic matter. These leaves must yield either directly or 

 indirectly organic acids, which help attack the soil, the minerals, and 

 the rocks with which they come in contact. 



The organic matter carried into their burrows by the termites con- 

 sists chiefly of the decayed wood and other vegetation eaten by them. 

 These materials, however, can not fail to contribute organic acids 

 that help attack the minerals of the soil and adjacent rocks. 



OPENINGS IN THE SOIL. 



The extensive subterranean excavations, especially those of the 

 true ants, permit the freer circulation of atmospheric air and of carbon 

 dioxide. These channels must also serve from time to time for the 

 passage of meteoric waters, and their great extent and ramification 

 must hasten very considerably all the processes of atmospheric disin- 

 tegration and alteration of soils., minerals, and rocks. 



Unfortunately we have no observations at present that enable us to 

 give quantitative values to these underground agencies and activities. 



