THE COMMUNITY OF THE ANTS 



the plants, and as they grow, surround their roots with yet more 

 earth. The advantage which the ants derive from this sort of garden- 

 ing is that their hanging nest is reinforced and anchored by the 

 roots of the plants. 



Another kind of Aztec ant inhabits the interior of the trunk of the 

 Imbauba-tree, and the extraordinary thing about these ants is that 

 the tree does half the ants' work for them (Fig. 32). On the exterior 

 of the slender stem we see, at short intervals, 

 little pits, which the ant has only to bore a 

 little deeper in order to obtain convenient 

 access to the interior. The interior of the tree is 

 hollow, and divided into chambers by lateral 

 partitions, and in these too the ants bore holes. 

 But the Imbauba-tree in question also provides 

 its guests with food. Under the axils of the large, 

 lobated leaves grow cushions of small egg-shaped 

 bodies. These are rich in oil and albumen, and 

 are eagerly devoured by the ants. The coloniza- 

 tion of the Imbauba-tree is effected as follows : 

 fertilized females make their way into the 

 chambers, and each founds a colony of her 

 own. Subsequently all these are united by 

 breaking through the dividing-walls ; the super- 

 fluous queens are killed, and only one remains, 

 who estabhshes herself in the upper part of the 

 trunk. There is only one species of Imbauba 

 that serves the ants as a dwelling. 



For a long while it was believed that the ants 

 and the tree stood in a relation of symbiosis, 

 inasmuch as the Imbauba offers the ants board 

 and lodging, while they protect its foliage from 

 Leafcutting ants and other enemies. Directly 

 one taps on the trunk the ants rush out, ready for battle. Recent 

 observations, however, have shown that the ants will allow other 

 insects to graze on the foUage undisturbed; even the Sloth is un- 

 molested ; and Woodpeckers are actually attracted by their presence. 

 We must assume, therefore, that the evolution of this "Ant- 

 Imbauba" has been conditioned by other factors, and that the Aztec 

 ants have merely acquired the instinct to make practical use of 

 the advantages which it offers. 



There are Acacias whose large hollow thorns provide dwellings 



319 



Fig. 32. — Section of 

 an Imbauba-tree, 

 inhabited by ants. 

 E, entrance - hole. 

 Beneath, the trunk 

 is laid open, in 

 order to show the 

 compartments, with 

 communicating 

 apertures; f, a 

 cushion of food. To 

 the right, a leaf of a 

 Tococa, with "ant- 

 pouches." {After 

 Schimper and Schit- 

 mann, reduced) 



