SOCIAL LIFE 247 



contrasting sets of instincts. While in the home nest they 

 sit about in stolid idleness or pass the long hours begging 

 their slaves for food or cleaning themselves and burnishing 

 their ruddy armour ; but when outside the nest on one of 

 their predatory expeditions they display a dazzling courage 

 and capacity for concerted action compared with which the 

 raids of sanguinea resemble the clumsy efforts of a lot of 

 untrained militia." The Amazons make their raids always 

 in the afternoon hours and Forel actually observed forty- 

 four raids on thirty afternoons during a period of seven 

 weeks after midsummer. He estimated the number of 

 amazon workers at 1000, and of the pupae captured by them 

 during the summer at 40,000. But only a small proportion 

 of these develop into slaves ; many are killed and eaten by 

 the Amazons while others are accidentally and fatally 

 injured in transport. 



Contrasted with these slave-making instincts are the 

 ways of certain ants which Wheeler defines as temporary or 

 permanent " social parasites." Communities of the former 

 group arise through the adoption of a young queen in a nest 

 of the host ants. F. Santschi (1920) describes how a newly 

 hatched female of the North African Bothriomyrmex de- 

 capitans is '' arrested " by workers of Tapinoma 7iigerrimum 

 when she approaches their nest, and dragged inside. If 

 any denizen threatens attack, she gets among the host- 

 larvae or on the back of the host- queen ; in such situations 

 her own characteristic odour is masked by that of the native 

 insects. The invader while on the back of the Tapinoma 

 queen may employ herself in biting off the latter's head 

 (hence the specific name, decapitans). The Bothriomyrmex 

 grubs are tended and fed by the Tapinoma workers ; these 

 ultimately die off, and as there is no host- queen left, the 

 mixed community is succeeded by a society composed 

 entirely of Bothriomyrmex. This cannot be started without 

 the help of Tapinoma, but when established it can carry 

 on independently, so that the parasitism is temporary. 



Among the permanent social parasites there is no worker 

 caste. The European Afiergates atratulus inhabits nests of 



