464 J. C. BRANNER — GEOLOGIC WORK OF ANTS 



dent of alighting from an aimless flight. Judging from the large num- 

 ber of individual females I have frequently seen in the air and on the 

 ground at one time, the great majority of these young colonies must fail 

 to survive. Often I have seen the young females so abundant 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 num- 

 ber of new colonies is started most of them must perish from mere over- 

 crowding, 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. Doctor 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 subsequent excavating is done by the con- 

 stantly increasing number of workers. As the colonies increase in num- 

 bers more underground room is required, and the amount of earth exca- 

 vated and carried to the surface increases proportionately. This earth is 

 brought to the surface in the form of small pellets in the jaws of the 

 workers, and 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, addi- 

 tions are constantly being made to these accumulations, and these addi- 

 tions 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 with- 

 out 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 he inferred that there would be prec- 

 tically 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 



28 Just how new colonies of saubas can be established by a single female is described 

 by Dr. J. Huber, in Biologisches Centralblatt, vol. xxv, pp. 606-618, 624-635, and in the 

 Boletim do Museu Goeldi, vol. v, pp. 223-241. Para, 1907-8. Also in the Annual Report 

 Of the Smithsonian Institution for 1906, pp. 355-367. 



