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EARTH MOVED BY ANTS 493 



GrEOLOGIC WORK 

 EARTH MOVED 



The amount of earth brought to the surface by ants in a few instances 

 has been given. The calculations at page 469 show that in one case the 

 earth brought up would cover the ground to a depth of 22.25 contimeters. 

 The estimate of Gounelle, mentioned at page 470, makes the earth brought 

 up 15 centimeters thick. In neither of these cases is it known how long 

 the building of the mounds occupied. 



Mr. Darwin's study showed that the earthworms in many parts of 

 England bring to the surface annually 10,516 kilograms of earth to the 

 acre.^^ In order to compare the work of ants with that of earthworms, 

 it would be necessary to know how long the ant-hills were in process of 

 formation. Unfortunately I have no trustworthy means of determining 

 the ages of the mounds. If we assume an average of 100 years for the 

 age of the mounds over the area measured (an average which seems to 

 me quite conservative in this case), the total work of worms and ants 

 would compare as follows : 



Total weight of earth brought to the surface in 100 years over 1 hec- 

 tare (10,000 square meters) : 



By worms in England 2,598,500 kilograms 



By ants in Brazil 3,226,250 kilograms 



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

 rather exceptional — that is, localities were selected favorable for exhibit- 

 ing 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, 



59 Charles Darwin : The formation of vegetable mould through the action of worms, p. 

 305. New York, 1882. 



