ANIMALS AND PLANTS 261 



insects or larger animals. One of the best known 

 cases of this kind is that of the tropical American 

 genus Cecropia, trees with large palmate leaves, some 

 species of which have the stems enlarged and hollow, 

 serving as the abode of certain ants which keep away 

 the leaf-cutting ants, which otherwise do great damage 

 to the tree by eating the foliage. The leaf-cutting 

 ants, in their turn, utilize the leaves for the formation of 

 miniature hotbeds upon which they are said actually to 

 cultivate a certain fungus which they use as food. Some 

 species of Acacia develop large hollow thorns, which 

 serve as shelters for ants which are also furnished with 

 food-bodies like those of Cecropia, and in return protect 

 their host against its animal foes. There are a number 

 of other more or less well-authenticated cases of myr- 

 mecophily. 



