PLANTS THAT KEEP AN ARMY 55 



extra protection to the acacia. Of course, their 

 milk cows, which are species of beetles, also a kind 

 of caterpillar, and cochineal, must be stationed 

 out in herds on various parts of the tree ; and each 

 herd is separated and carefully guarded by a herds- 

 man; and he, in turn, is accompanied by several 

 small animals, obviously as watch-dogs. As a 

 colony of ants and their helpers are capable of 

 destroying hundreds of caterpillars and grasshop- 

 pers a day, and as they work day and night, the 

 tree is well protected. 



In still another way do the servants of the plant 

 prove a benefit to it: in addition to destroying or 

 driving away the larger marauders they eat the 

 minute parasites. 



There are plants which do not produce honey 

 with which to pay their armies ; in such a case it is 

 usually found that the plant is already inhabited 

 by a number of insects, which can supply milk and 

 meat to the warrior inhabitants ; and so slave-hold- 

 ing ants take possession of the tree as a desirable 

 dwelling-place on which to raise their army of 

 allies. One form of beetle, raised in the under- 

 ground nests of these ants, secretes and produces 

 a sweet fluid, that might be an intoxicant. 



Another plant of the tropical regions which 

 keeps not only its own standing army, but also its 



