SLAVE-MAKING ANTS 81 



one side or the other. It attaches itself under the middle 

 of the ant's head. The mite eats the food of the ant, but 

 does not injure it individually ; for anything that prevented 

 the ant seeking its food would directly injure the parasite. 

 When the ant feeds, the mite moves forward slightly, and 

 takes its share of food from the ant's tongue. 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 arrange themselves one on 

 either side and one in the middle, and if one drops off the 

 remaining two arrange themselves accordingly. 1 Are these 

 instinctive actions conceivable as the outcome of a muta- 

 tion ? Hardly, unless of a long series of minute mutations 

 indistinguishable from fluctuating 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-owners we find 

 gradations between those which are often without any 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 expeditions are made in which the 

 nests of other ants are attacked, 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 household 

 duties in the absence of slaves. Polyergus rufescens has 

 gone further 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, 



1 Janet, Ch., Etudes sur les fourmis, les gutpes et let abeillcs, note 13 ; Sur 

 le Lasius mia-tus et V Antennophorus uMmanni, &c., Limoges, 1897. 



F 



