86 TROPICAL NATURE, AND OTHER ESSAYS. 



direction. When in the island of Marajo, near Para, I 

 noticed a path along which a stream of Salibas were 

 carrying leaves from a neighbouring thicket ; and a 

 relation of the proprietor assured me that he had known 

 that identical path to be in constant use by the ants for 

 twenty years. Thus we can account for the fact mentioned 

 by Mr. Bates, that the underground galleries were traced 

 by smoke for a distance of seventy yards in the Botanic 

 Gardens at Para ; and for the still more extraordinary 

 fact related by the Kev. Hamlet Clark, that an allied 

 species in Rio de Janeiro has excavated a tunnel under 

 the bed of the river Parahyba, where it is about a quarter 

 of a mile wide ! These ants seem to prefer introduced 

 to native trees ; and young plantations of orange, coffee, 

 or mango trees are sometimes destroyed by them, so 

 that where they abound cultivation of any kind becomes 

 almost impossible. Mr. Belt ingeniously accounts for 

 this preference, by supposing that for ages there has 

 been a kind of struggle going on between the trees and 

 the ants ; those varieties of trees which were in any way 

 distasteful or unsuitable escaping destruction, while the 

 ants were becoming slowly adapted to attack new trees. 

 Thus in time the great majority of native trees have 

 acquired some protection against the ants, while foreign 

 trees, not having been so modified, are more likely to be 

 suitable for their purposes. Mr. Belt carried on war 

 against them for four years to protect his garden in 

 Nicaragua, and found that carbolic acid and corrosive 

 sublimate were most effectual in destroying or driving 

 them away. 



The use to which the ants put the immense quantities 

 of leaves they carry away has been a, great puzzle, and 



