SOCIAL PARASITES 



Although most of the nursing in the sanguinea nest is 

 done by the slaves, at least in those colonies which have them, 

 the species is not at all degenerate. The workers are fully- 

 capable of running the whole colony if necessary ; they are 

 extremely active and, judging by their behaviour on raids, 

 very well endowed. Nevertheless, it is probable that the 

 behaviour of some of the more degenerate parasites described 

 in the next few paragraphs developed out of slave-raiding. 

 Once the ability to run the colony independently has been 

 lost it is evidently very difficult to regain it. 



Heads of some wprkers of ants and of their slavemakers or para- 

 sites. A, the slave-maker, Formica sanguinea; B, its slave, Formica 

 fusca; C, the amazon ant, Polyergus rufescens; D, Strongylog- 

 nathus, parasite; E, Tetramorium, host. The mandibles of types C 

 and D are suitable only for offence; such ants have to be fed by 

 their slaves or hosts. 



This is seen in the more specialised slave-keeping ants 

 known as the amazons, the various species of Polyergus. 

 Some of these are found in western Europe (France, Switzer- 

 land), others all the way across central Asia to Japan and 

 again in North America. 



The mandibles of the amazons are sickle-shaped and 

 pointed, without the broad, finely-toothed edge of those of 

 an ordinary ant. These jaws are unsuited for anything but 

 fighting, and the amazons are incapable of making a nest or 

 of looking after their own young. The tongue-like organ of 

 the mouthparts is also short, and they are almost incapable 



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