312 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
the ground at one time, the great majority of these young colonies 
must fail to survive. Often I have seen the young females so’abun- 
dant that there must have been an individual to every square meter 
of land surface over areas of many hundreds of acres. 
In some places where the new arrivals alight the mounds are 
already so thick that there is little or no room for new colonies, and 
it is probable that some of these young females must either be adopted 
into the old colonies or they are killed or die.! 
It is evident from the nature of the case that where such a large 
number of new colonies is started most of them must perish from 
mere overcrowding, if for no other reason. 
The excavation first made by a young female is small and simple, 
and the earth taken from it is heaped about the opening without 
any apparent order. Dr. Huber, in the paper just cited, states that 
at Para, in a colony started by a single female, the first workers 
appear at the end of 40 days. Shortly thereafter the queen, or 
founder of the colony, ceases to be an active worker, and all subse- 
quent excavating is done by the constantly increasing number of 
workers. As the colonies increase in numbers more underground 
room is required, and the amount of earth excavated and carried to 
the surface increases proportionately. This earth is brought to the 
surface in the jaws of the workers in the form of small pellets which 
are thrown down apparently without any other object than to be rid 
of them. Sometimes they are heaped up in funnel-shaped pits; 
sometimes they are thrown out on the downhill side of the opening. 
At first these bits of earth form heaps of loose, incoherent material, 
but in time, and with rain and sunshine, it packs down until it is 
often as hard as an unbaked brick. As long as the colony is active 
and growing, additions are constantly being made to these accumu- 
lations, and these additions may be at any point over the sides or 
at the top. Passageways are either kept open through these heaps 
of earth or they are reexcavated. This is demonstrated by digging 
into the mounds, but it is evident without opening them, from the 
fact that the fresh material is brought out and spread over any and 
all parts of the surface. 
Size of the mounds.—It mught be wnifaeted that there would be 
practically no limit to the size of the mounds built in this fashion, 
and I am not sure that there are any limits save those which may be 
imposed by certain physical conditions, such as the amount and dis- 
tribution of the rains, the character of the soil, the area over which 
the necessary plants or food can be obtained, etc. Of course, the 
mounds are of different sizes according to their ages; but consid- 
1 Just how new colonies of saubas can be established by a single female is described by Dr. J. Huber in 
Biologisches Centralblatt, vol. 25, pp. 606-618, 624-635, and in the Boletim do Museu Goeldi, vol. 5, pp. 
223-241. Para, 1907-8. Also in the Annual Report of the Smithsonian Institution for 1906, pp. 355-367. 
