IV ON PLANT LIFE 157 



plant is by no means the only service which 

 insects render. 



Ants, for instance, are in many cases very 

 useful to plants. They destroy immense 

 numbers of caterpillars and other insects. 

 Forel observing a large Ants' nest counted 

 more than 28 insects brought in as food per 

 minute. In some cases Ants attach them- 

 selves to particular trees, constituting a sort 

 of bodyguard. A species of Acacia, described 

 by Belt, bears hollow thorns, while each leaflet 

 produces honey in a crater-formed gland at 

 the base, as well as a small, sweet, pear- 

 shaped body at the tip. In consequence it 

 is inhabited by myriads of a small ant, which 

 nests in the hollow thorns, and thus finds 

 meat, drink, and lodging all provided for it. 

 These ants are continually roaming over the 

 plant, and constitute a most efl&cient body- 

 guard, not only driving off the leaf-eating 

 ants, but, in Belt's opinion, rendering the 

 leaves less liable to be eaten by herbivorous 

 mammalia. Delpino mentions that on one 

 occasion he was gathering a flower of Clero- 

 dendrum, when he was himself suddenly 

 attacked by a whole army of small ants. 



