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. 
