316 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
The figures obtained are given in the table below: 
Table of areas and cubical contents of mounds of different sizes within an area of 10,000 
square meters, 
[All measurements are in meters. ] 
| | | 
| Area of Total con- 
Number of} Diameter | each in Fotal ares Heicht Cubical tents in 
mounds. | otbase. | square | “3 Sd0") ent. | contents. eubic 
| meters. <e2 meters. 
—_——-|— ae rae a aT ae 
Lal 15 176. 71 176.71 4.5 265 265 
2 11 95. 03 190. 06 4.2 133 266 
6 10 78. 54 471, 24 3.9 102 612 
84 8 50. 26 402. 08 3.1 51 408 
12 | U 38. 48 460. 76 2.9 37 444 
5 6 28. 27 141.35 2.3 21 105 
4 5 19. 63 78. 52 2.0 3 52 
gl 4 12. 56 87.92 7 7 49 
8 | a 7. 06 56. 48 1.2 3 24 
| 
Sy bem anes oe oy al eee a 2, 225 
| 
This estimate makes the area actually covered by the mounds close 
to one-fifth of the total area under consideration. My notes show 
that within areas of a few acres the ground covered by the mounds is 
sometimes as high as one-half of the total area. The cubical con- 
tents of. the mounds, if evenly distributed over the entire 10,000 
square meters, would have a thickness of 22.25 centimeters. 
Although the mounds within the area here considered were large, 
they were not the biggest I have seen, nor do they average as large as 
can befound. The largest ones measured were on the upper drainage 
of Rio Utinga; several of these were found to be 5 meters high and 
16 and 17 meters-in diameter at the base, and each contained, there- 
fore, about 340 cubic meters of earth. There were no other mounds 
closer to these than 10 or 15 meters. 
The reader should be reminded, however, that this sort of thing 
is not to be seen in all parts of the country, by any manner of means. 
So far as my own observations go, ant mounds are unusually large 
and unusually abundant in this particular part of Brazil. 
Age of the mounds.—The amount of work done by these ants in a 
region where they seem to be favorably located is fairly well shown in 
the preceding table. Trustworthy data for calculating the time 
required to build a mound of a given size or to do any given amount 
of work are lacking. Necessarily the time must vary with the size of 
the colonies, other things being equal. The colonies, however, 
appear to have their ups and downs, for while some of them increase 
in numbers and continue to add to the mounds for long periods, 
others appear to be less active, while still others disappear, whether 
by migrating or through the death or captivity of the members 
is not certainly known at present. It is interesting to note that the 
Brazilians generally regard the size of the ant hill as directly related 
