158 On Plants and Insects. 



the hollow thorns, and thus find meat, drink, and 

 lodging all provided for them. These ants are conti- 

 nually roaming over the plant, and constitute a most 

 efficient body-guard, not only driving off the leaf- 

 cuttingants, but, in Belt's opinion, renderingthe leaves 

 less liable to be eaten by herbivorous mammalia. 



5. I am not aware that any of our English plants 

 are protected in this manner from browsing quad- 

 rupeds, but not the less do our ants perform for 

 them a very similar function, by keeping down the 

 number of small insects, which would otherwise rob 

 them of their sap and strip them of their leaves. 



Forel watched, from this point of view, a nest of 

 ants. He found that they brought in dead insects, 

 small caterpillars, grasshoppers, cercopis, &c., at 

 the rate of about 28 a minute, of more than 1600 

 in an hour. When it is considered that the ants 

 work, not only all day, but in warm weather, often 

 all night too, it is easy to see how important a 

 function they fulfil in keeping down the number of 

 small insects. 



6. Some of the most mischievous insects, indeed 

 certain species, for instance, of green fly and scale 

 insect have turned the tables on the plants, and 

 converted ants from enemies into friends, by them- 

 selves developing nectaries and secreting honey, 

 which the ants love. We have all seen the little 

 brown Garden Ant, for instance, assiduously run- 

 ning up the stems of plants, to milk their curious 

 little cattle. In this manner, not only do the 



