GEOLOGIC WORK OF ANTS — BRANNER. 



331 



and not of earth. Those on trunks, only a meter or two above the 

 ground, are often made partly of woody matter and partly of earth. 



GEOLOGIC WORK. 



EARTH MOVED. 



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

 instances has been given. The calculations at page 316 show that in 

 one case the earth brought up would cover the ground to a depth of 

 22.25 centimeters. An estimate by Gounelle * makes the earth brought 

 up 1 5 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 



Fig. 10.— White ants' nest in a tree, Salitre Valley, State of Bahia. 

 [J. C Branner, 1907.) 



acre. 2 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 deter- 

 mining 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 hectare (10,000 square meters) : 



Kilograms. 



By worms in England 2, 598, 500 



By ants in Brazil 3, 226, 250 



i E. Gounelle: Ann. Loc. Entom. France, 7 ser. No. 6, 1896, pp. 332-333. 

 1 Charles Darwin: The formation of vegetable mold through the action of worms, p. 305. 

 18S2. 



New York, 



