GEOLOGIC WORK OF ANTS—BRANNER. 815 
In some places they stand so close that their bases touch each other, 
though such cases appear to be rather exceptional. The mounds in 
this part of Minas and Bahia that appear to have reached their full 
development range from 1 to 44 meters in height and from 3 to 10 
meters in diameter at the base. The biggest of these mounds— 
that is, one 4.5 meters high and 10 meters in diameter—contains 
approximately 117 cubic meters of earth. 
At one place in the Rio Utinga region, where the forests had been 
cleared away so that the mounds were clearly visible, I selected a 
nS CLS al 
Fic. 2.—Ant hill (Formiga de mandioca) near Mundo Novo, State of Bahia, Brazil. 
[¥rom a photograph by R. Crandall, 1907.] 
spot where they were strikingly abundant, and measuring a space 
100 by 100 meters, as nearly as it could be done by pacing, counted 
the mounds within the area and estimated their heights and diam- 
eters at the base. \ 
The slopes of these mounds vary from less than 30 degrees up to 47 
degrees, and on some parts of them there are even perpendicular 
places. It was thought that 38 degrees was a fair average for the 
ones in this particular area. 
