126 INSECTS 



servants to do their work; and yet even this is a matter 

 of domestic economy to be covered rather by a 

 student who, like Dr. William Morton Wheeler, has 

 studied the ants in their relation to each other, than 

 by a general work, dealing rather with the relations 

 of different kinds of insects. 



In the domestic economy of ants, we have to con- 

 sider those species which are of use to the ants them- 

 selves and are fostered and cultivated for that reason, 

 and those that maintain themselves in the nests in 

 spite of opposition or by toleration only. The first 

 series are those from which the ants derive a direct 

 benefit; the others are those which do them no direct 

 harm and rather indirectly benefit them. 



Perhaps plant lice are the best known of those 

 that are directly fostered, and they are favored because 

 of the saccharine secretion or "honey" which they 

 produce. The simplest form of this relation is where ants 

 visit colonies of plant lice on vegetation and, by stim- 

 ulating or irritating the specimens with their antennae, 

 induce them to eject a drop of the sweet secretion which 

 is then gathered up. In return the ants attack and 

 drive off a great many enemies that would otherwise 

 destroy their herds. The next stage is when ants 

 build galleries around roots infested by plant lice and 

 directly favor them by freeing from soil and other in- 

 cumbrances an abundance of feeding surface. This 

 would seem to give the plant lice a free field for increase ; 

 but not only do parasites find their way into the nests 

 but even larvae of ladybird beetles occur in consider- 

 able numbers. These latter, however, in almost every 

 case, produce from specialized glandular structures, 

 waxy fibres which seem almost or quite as attractive 

 to the ants as the secretions of the plant lice. They 

 therefore feed upon these processes or rather excre- 



