328 



ANNUAL. REPORT SMITHSONIAN INSTITUTION, 1911. 



In the region about the headwaters of the Paraguay the nests of the 

 white ants are extremely abundant in favorable localities, and the 

 forms of the nests are different from those noted in other parts of trop- 

 ical America. The tall and very slender forms are especially notice- 

 able in the low, flat prairie lands south of Cuiaba. (See fig. 8.) These 

 slender forms are known in that part of Brazil by the Indian name of 

 tacuru. 



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

 habits 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 





Mi 





Fig. 8.— White ants' nest of earth in Matto Grosso, on the plains of the Upper Paraguay. 

 [Sketch by J. C Branner.] 



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 years 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 building 

 may have been very different. 



UNDERGROUND STRUCTURES. 



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

 ground, passageways, but wherever I have seen these passageways 

 opened they appeared to have been excavated and then to have been 



