iv SOCIAL HOMES H9 



progress. Finding one sufficiently advanced they 

 bite through its small point of attachment with the 

 pinnule,* and, bending it down, break it and bear it 

 off to the nest. Like the glands the fruits do not 

 ripen at once, but successively, keeping the ants in 

 protracted attendance upon the new leaves. 



In this way the formic visitors are brought to act 

 as the standing army of the acacia, at the season of 

 the year when it is fresh and sweet and most liable 

 to attack, in return for all the comforts and 

 luxuries that it bountifully affords. Provided with 

 severe stings the protectors preserve the leaves from 

 the browsing of mammalia, and from the ravages of 

 much more dangerous enemies, the leaf-cutting ants ; 

 nor can a caterpillar venture to approach without 

 suffering from the weapons of the plant's body-guard. 

 Even should the aggressor be man, and if he touches 

 or shakes a branch, they swarm out, making free use 

 of their jaws and sting. To all appearances they 

 lead the happiest of existences. They fear no 

 foe, they have ample food, and accommodation all 

 that heart could desire. But there is a reverse side 

 to this happy picture. In the dry season on the 

 plains the acacias cease to grow, no young leaves are 

 produced, and the glands, now old, secrete no delicious 

 honey. Then the ants perish miserably from want 

 and hunger, and many of the thorns become 

 depopulated. Again, when the rains set in, the buds 

 burst forth with all their dainties to the ant palate, 

 and accordingly once more the creatures multiply. 



Both in Brazil and Nicaragua the flower-buds and 

 young leaves of numerous plants are exempt from the 



