GEOLOGIC WORK OF ANTS—BRANNER. 317 
to the age of the colony. At Serrinha, on the Sao Francisco Railway, 
I was told that mounds about 2 meters high and having a base of 
about 5 meters were probably as much as a hundred years old. 
This was an expression of views based simply upon a general impres- 
sion and not upon records. 
UNDERGROUND WORK. 
So far as I can learn, there has never been any careful examination 
or study of the character, extent, and uses of the underground excava- 
tions made by ants in the Tropics. What is known about them 
has been learned accidentally, and our knowledge of the passages is, 
therefore, fragmentary. I have frequently dug into the mounds, 
Fic. 3.—Ant hills made by the “ Formiga de mandioca,” near Ventura, State of Bahia, Brazil. 
{From a photograph by R. Crandall, 1907.] 
but always without the time necessary for satisfactory results. The 
most I have been able to make out in these hasty explorations is 
that the superficial mounds are penetrated in every direction with 
passageways. The large mounds were in no case opened down to the 
original surface of the ground; but when small mounds were opened 
they were found to connect through small tunnels with the under- 
ground excavations. 
A pit started by the removal of a large ant hill east of Timbo, in the 
interior of Bahia, and continued to a depth of about 4 meters, showed 
the arrangement of the underground tunnels better than I have seen it 
