68 ANIMAL BIOLOGY 



of the slave-making species which regularly make excur- 

 sions against other communities, and after killing off 

 or driving away the inhabitants, seize the pupae and carry 

 them back to their own nests. Here when the young 

 ants emerge they are adopted by their captors and take 

 part in the household and other duties as if to the manner 

 born. In some cases, as in the Amazon ant, Polyergus 

 rufescens, the ants have come to be dependent upon their 

 slaves for their subsistence. The Amazons have large 

 curved jaws especially fitted for fighting, but they have 

 lost the power of food gathering and would perish were 

 they not fed by their faithful slaves. They have become 

 so specialized as warriors that they have become useless 

 for all other tasks. In addition to their slaves, ants 

 sometimes harbor in their nests a motley assemblage 

 of other creatures which are often spoken of as " guests" 

 or commensals. We have already spoken of the aphids 

 or "ant cows" from which the ants obtain a sweet juice. 

 Ants also harbor many species of beetles including several 

 blind forms; these are cleaned and fed by their hosts with 

 as much care as is bestowed upon members of their own 

 family. In return the ants obtain a secretion from these 

 guests. In many cases the inmates of the nest seem to 

 be simply tolerated without affording the ants any com- 

 pensation for their board and lodging. There are known 

 to be over one thousand species of insects which live for 

 all or a part of their lives in the nests of ants, and many 

 of them show very curious adaptations to this mode of life. 

 Ants are sometimes a source of considerable annoyance 

 to man. The little red ants that come into houses and 

 delight in getting into the sugar and other articles of food 

 are often difficult to deal with on account of their small 

 size. The best way to check them is to follow up their 

 runway to the nest and then flood the insects with kero- 



