TERMITE STRUCTURES 479 



diers in obstructing the passage of the ants into the termites' nests and 

 galleries. 



The result of the relations existing between the true ants and the 

 termites is that the two kinds do not thrive together; at least I have 

 never found the termites' nests where the saubas or other true ants were 

 notabh^ abundant. Preyed on by the true ants and by animals of so 

 many different kinds, and even by insects themselves, it occurs to one 

 that their chances of survival in the midst of so many enemies must be 

 very small. That survival appears to be due largely to their habit of 

 living and working under the protection of their covered roadways, and 

 to the fact that their roads are constructed of materials that are remark- 

 ably inconspicuous. N^othing could look more thoroughly abandoned 

 and lifeless than the common run of white ants' nests and their covered 

 passages; yet if one breaks through these coverings he will usually find 

 them fairly swarming with life. 



My general impression is that those white ants which build mounds of 

 earth are especially abundant in the highlands of Minas Geraes and 

 through the semi-arid portions of Sergipe, Bahia, Goyaz, Matto Grosso, 

 and the interior of Ceara, Maranhao, and Piauhy. Mr. Crandall tells 

 me that he finds them most common on the Diamantina plateau. (Let- 

 ter of June 23, 1909.) 



STRUCTURES ABOVE GROUND 



General char act eristics. — The nests of the white ants, or cupim, have 

 no visible external openings. When a mound is new or is being added 

 to, the outside of the new portion is so soft that it can be readily broken 

 off with a stick; but with time the outside usually becomes as hard as a 

 brick. This hard outside covers the entire mound, and is usually about 

 6 inches thick, but in the very big nests it is sometimes nearly or quite a 

 foot thick. Inside of this hard, thick covering the materials are quite 

 soft and brittle, and the partitions are sometimes almost as thin as paper, 

 though thicker in the larger nests. Where the mound stands on the 

 ground, the cavities of the upper portion connect through the perforated 

 base with subterranean excavations. 



Parts of the nests are made of the excrement of the inhabitants. I 

 have often broken the nests or the covered roads of these insects in order 

 to observe the workers repair them. In every case observed the repairs 

 were made by building up a wall or covering of excrement or something 

 of the kind. At least it is voided from the posterior part of the body in 

 a plastic condition, and is smoothed down on the sides so that the later 

 layers alwa3^s override the earlier ones on both sides of the wall. An ex- 



