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. 1 



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 apparent^ 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 reexcavatecl. 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 might be inferred 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. 609-618, 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. 



