THE SOCIAL INSECTS 



of small insects such as caterpillars. It may also find small 

 dead insects which are worth collecting. Ants are always a 

 serious nuisance to solitary wasps whose prey is stolen while 

 awaiting storage in the wasp's nest. But the wood ant also 

 collects large quantities of aphis excreta. Okland has cal- 

 culated that a large nest in Sweden may collect as much as 

 20 lb. of dry sugar in a season ; this means a very much 

 larger quantity of the liquid excreta. As a rule, hunting 

 workers act singly, so that the prey are no bigger than one 

 ant can overpower and carry by itself. In some ants, how- 

 ever, the workers co-operate to overpower much larger 

 insects, such as big beetles or even small birds. 



Hingston has described how this is done by an Indian 

 ant, Oecophylla smaragdina. One of a number of hunting 

 workers happens to find a beetle and seizes one leg. It is too 

 powerful for the one worker. There is a struggle which soon 

 attracts others. Each one seizes some projecting part and 

 pulls, and soon the beetle is splayed out with all its members 

 pulled in different directions. The ants continue a steady 

 pull, if necessary for half an hour, until the prey is dead. The 

 workers then co-operate to bring it home; most of them pull 

 the legs on one side, but a few remain on the other side to 

 steady it. In this way it will be dragged home even if the nest 

 is high up in a tree. 



There is one group of ants, the Ponerines, which are pre- 

 eminently hunters. Very few of them collect aphis excreta 

 or are attracted to sweet substances, though a few of them 

 feed, at least partly, on seeds. In structure the Ponerines are 

 the least specialised of the ants, in many ways most like what 

 we imagine the ancestors of the whole group to have been. 

 Both in their addiction to hunting living prey, in the small 

 size of their colonies, and in other features they seem to be 

 more primitive than other ants. They are now relatively 



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