GEOLOGIC WORK OF ANTS—BRANNER. S81 
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 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 
Fig. 10,— White ants’ nest in a tree, Salitre Valley, State of Bahia. 
(J. C. Branner, 1907.) 
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 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. 
dS VaWoree ia SNC IAI Go. /:o a. Fo) aiafn do ope = alate renin 2, 598, 500 
Ryman area esther eee ee Bere. eee ae ace sic 3, 226, 250 
1E, 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. New York, 
3882, 
