488 J. C. BRANNER GEOLOGIC WORK OF ANTS 



true ants excavate their tunnels in the earth they depend on the character 

 of the ground and the form of the excavations to support the structures. 

 The white ants, on the other hand, depend partly on the nature of the 

 soil, but partly on their method of cementing the materials of which their 

 nests are made. 



The preference, however, of the termites for certain soils and certain 

 localities is very evident in some districts. On the upper Paraguay 

 places have been seen where the nests are quite thick over certain areas, 

 while there were none, or but few, on an adjoining area. Wherever these 

 marked contrasts have been observed, however, they have apparently been 

 due to a difference in the amount of moisture in the ground. I have 

 thought that the white ants are sometimes found in rather wet ground, 

 because they are there comparatively free from the attacks of their ene- 

 mies, the true ants. 



Opinions of Brazilians in regard to the distribution of the termites' 

 nests vary considerably; some think they are more abundant in the open 

 campo regions than in the forests; others think they prefer fields; still 

 others think they are favored by a dry climate. All of these views appear 

 to have more or less support. I have much doubt, however, about the 

 theory of their preferences for campos. It is true that they do appear 

 very abundant in the campo regions, but I am of the opinion that the 

 apparent abundance is deceptive and due to the fact that all the nests arc 

 visible at once over a wide area (see plate 35, figure 2), while in a forest- 

 covered area no nests, or but few nests, can be seen on account of their 

 being concealed by the dense vegetation. This impression has been 

 deepened by the fact that in several instances where the forests have been 

 cleared away the mounds of the white ants appear to be quite as abun- 

 dant as they are in the old clearings or on the open campos. 



Further support is given this theory by Maximilien, Prince de Wied- 

 Neuwied, who, in speaking of the Avhite ants' nests near Conquista, in 

 the southwestern part of the State of Bahia, says that they are extremely 

 abundant in covered and wooded places. '^'^ 



RELATIONS TO VEGETATION 



Compared with the true ants, the white ants are harmless. At least 

 they do not attack crops and animals or render certain localities unin- 

 habitable. The harm they do to agriculture is confined to the mere 

 encumbrance of the ground by their big, hard, rock-like nests. They do, 

 however, destroy wood used in the construction of fences, houses, bridges, 



Voyage au Bresil, vol. lii, p. 129. Paris, 1822. 



