WHAT IS INTELLIGENCE? 201 



slightly, and takes its share of food from the ant's tongupii 

 Should a second mite attach itself to an ant, the first 

 moves over to one side and the second takes up a position 

 upon the opposite side, thus keeping the ant well balanced 

 and hampering its movements as little as possible. Should 

 one of the mites drop off, the other moves to the middle. 

 When three mites attach themselves to one ant they ar- 

 range themselves one on either side and one in the middle, 

 and if one drops off the remaining two arrange themselves 

 accordingly. Are these instinctive actions conceivable as 

 the outcome of a mutation? Hardly, unless of a long ser- 

 ies of minute mutations indistinguishable from fluctuat- 

 ing variations. 



"Among the ants we find, besides species that live in 

 colonies in an independent manner, species that make 

 slaves of other species of ants. Among these slave own- 

 ers we find gradations between those which are often 

 without slaves and perfectly able to look after themselves 

 and their young, and those which are not able to feed 

 themselves or even to fight. Formica sanguinea is the 

 only slave-making ant' in Great Britain. Regular expe- 

 ditions are made in which the nests of other ants are at- 

 tacked, and the pupae are carried off by the conquerors. 

 When the pupae hatch out they do most of the house- 

 work for their owners, who are very lazy. There are 

 workers, however, who do the housework duties in the 

 absence of the slaves. Polyergus rufescens has gone fur- 

 ther in the slave-owning direction than F. sanguinea. It 

 is admirably adapted to its part. While F. sanguinea is 

 not really a great warrior, and fights only in numbers, P. 

 rufescens does not mind any odds, and fights single- 

 handed most splendidly. When in an attacking force, 

 however, these ants act in concert in the most remarkable 

 manner, the fierceness of the individual being subordin- 



