in ANIMAL LIFE IN THE TROPICAL FORESTS 285 



veritable ants' nests. When very young the stems are like 

 small, irregular, prickly tubers, in the hollows of which ants 

 establish themselves ; and these in time grow into irregular 

 masses the size of large gourds, completely honeycombed with 

 the cells of ants. 1 In America there are some analogous cases 

 occurring in several families of plants, one of the most 

 remarkable being that of certain Melastomas which have a 

 kind of pouch formed by an enlargement of the petiole of 

 the leaf, and which is inhabited by a colony of small ants. 

 The hollow stems of the Cecropias (curious trees with pale 

 bark and large palmate leaves which are white beneath) are 

 always tenanted by ants, which make small entrance holes 

 through the bark ; but here there seems no special adaptation 

 to the wants of the insect. In a species of Acacia observed 

 by Mr. Belt, the thorns are immensely large and hollow, and 

 are always tenanted by ants. When young these thorns are 

 soft and full of a sweetish pulpy substance, so that when the 

 ants first take possession they find a store of food in their 

 house. Afterwards they find a special provision of honey- 

 glands on the leaf -stalks, and also small yellow fruit- like 

 bodies which are eaten by the ants ; and this supply of food 

 permanently attaches them to the plant. Mr. Belt believes, 

 after much careful observation, that these ants protect the 

 plant they live on from leaf-eating insects, especially from the 

 destructive Saiiba ants, that they are in fact a standing 

 army kept for the protection of the plant ! This view is 

 supported by the fact that other plants Passion-flowers for 

 example have honey-secreting glands on the young leaves 

 and on the sepals of the flower-buds which constantly attract 

 a small black ant. If this view is correct, we see that the 

 need of escaping from the destructive attacks of the leaf- 

 cutting ants has led to strange modifications in many plants. 

 Those in which the foliage was especially attractive to these 

 enemies were soon weeded out unless variations occurred which 

 tended to preserve them. Hence the curious phenomenon of 

 insects specially attracted to certain plants to protect them 

 from other insects ; and the existence of the destructive leaf- 



1 These form two genera, Myrmecodia and Hydnophytum. For descrip- 

 tion and figures see Mr. H. 0. Forbes' Naturalist's Wanderings in the Eastern 

 Archipelago, p. 79. 



