TERMITE STRUCTURES 487 



spondiug region underground, they are built into a mesbwork of tunnels, 

 galleries, and cbambers, where the social interests of the community are 

 attended to." 



Age of the mounds. — The method of building the mounds and the 

 haljits of the termites, so far as I am acquainted with them, lead to the 

 conclusion that the size of a mound is determined by its age and by the 

 size of the colony building it. Just how long it requires to build the 

 large mounds I have but little means of judging. One frequently sees 

 nests built on houses and fences, and in these cases it has been possible 

 to determine the maximum ages of these particular nests. These cases, 

 however, afford only a suggestion. The oldest nests I have seen, and of 

 which I could get an idea of their ages, were not more than 50 jeavs old, 

 and the biggest of them contained a little less than 1 cubic meter of 

 earth, the estimate being made without reference to the cavities within 

 the mass. 



It is evident that the size and age in one of these cases may or may 

 not help one to determine the time occupied in the construction of one 

 of the. very large nests figured in this paper, for the rates of buildjng 

 may have been very different. 



UNDERGROUND STRUCTURES 



The above-ground structures of the white ants connect Avith under- 

 ground passageways, but wherever I have seen these passageways opened 

 they appear to have been excavated and then to have been filled with 

 smaller chambers made of materials like that used to make the chambers 

 of the mounds above ground. An examination of the thin chamber walls 

 found in some of the underground excavations shows that they have been 

 constructed of soft, plastic materials so piled up that each later addition 

 overlaps the preceding one on both sides of the wall. The materials are 

 partly of reddish clay like that of the ground in which the nest is made, 

 and partly of a dark brown substance tliat I take to be organic matter — 

 probably masticated plants. 



I have never seen the excavations made by the white ants more than a 

 meter and a half below the surface, but I have heard of them being found 

 considerably deeper. My friend, Dr. Joaquim Lustosa, of Lafayette, 

 State of Minas Geraes, writes me on this subject : "As for the depth to 

 which they penetrate the ground, it is my impression that it is but little 

 more than 3 metres." 



RELATION OF NESTS TO THE SOIL 



The white ants do not seem to be so dependent on the character of the 

 soil as do the true ants. This is probably due to the fact that when the 



