318 



ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 



elsewhere. Tlie section did not pass through the main shaft or tunnel 

 that connected the ant hill with the subterranean excavations, but a 

 little to one side of it. The upper layer of the earth, to a depth of 

 half a meter, was undisturbed ; then there was one tunnel with a flat 

 floor, about 20 to 25 centimeters across, and having a low arched 

 roof; below this, at a distance of about 25 centimeters, were two 

 tunnels at the same level and of about the same size and shape: 

 below these, at a further depth of about 25 centimeters, were three 

 similar openings. This arrangement continued to a depth of nearly 

 2 meters, the tunnels being more numerous always at the lower 

 levels. The tunnels at the lowest level did not form a complete 

 row, but the work seemed to have been commenced at the outside. 



This same arrangement of the tunnels has been seen frequently in 

 railway cuts and ditches, but nowhere else have I seen so many levels 

 or such a clearly defined plan in the placing of the excavations. 



In some other cases noted the number of tunnels connecting the 

 above-ground mounds with the underground galleries seemed to vary 



Fig. 4.— Nest of leaf-cutting ant. 

 After Belt. "The Naturalist in Nicaragua," p. 80. 



with the size of the mounds — that is, the more ground the mound 

 covered, the more passageways there seemed to be to connect with the 

 galleries beneath. 



The section through the burrows given by Belt is reproduced in 

 figure 4. This section, however, is diagrammatic, and does not claim 

 to show the great extent of the galleries. Belt tells, however, of 

 galleries 1.5 meters in depth (p. 76). The best evidence I have 

 been able to gather hi regard to the depth to which the ants penetrate 

 has been obtained in cuts along railways and canals, and in deep 

 ditches often dug to serve as fences. On Rio do Peixe, near Serro, 

 in the State of Minas Geraes, I found the galleries as deep as 2.5 meters 

 at several places along a canal under construction. Most of them, 

 however, were only about 1.5 meters below the surface at the deepest 

 points exposed. At Bomfim, on the Bahia and Sao Francisco 

 Railway, I found the burrows exposed in a deep ditch at a depth of 

 2.1 meters. 



