THE SOCIAL INSECTS 



the habit of catching the numerous insects trying to escape 

 the ants; the birds themselves escape both by their size and 

 mobility. One can, in fact, stand still in the middle of a 

 raiding army and come to no harm if one moves on every 

 minute or two. But there is no such escape for any insect or 

 small animal which cannot fly away. Wasps' nests, for 

 instance, are deserted and the whole brood is captured. 



The African driver ants are even more formidable and will 

 kill even pigs and fowls if these are enclosed. They have 

 been known to devour a large python which was so gorged 

 after a meal that it could not escape. These ants will enter 

 houses and clear them entirely of the vermin, such as cock- 

 roaches and spiders. Fortunately, human food other than 

 meat does not attract them, so that their visit is on the whole 

 beneficial, at least in retrospect. 



Most driver and legionary ants construct only temporary 

 nests. Often they occupy some natural hole or crevice, such 

 as may be found at the roots of a large tree. Some of them 

 have the faculty of building a structure by using the bodies 

 of some of the workers themselves. By hanging onto one 

 another long chains can be formed, and the chains may be 

 arranged to arch over and enclose spaces. In this way a 

 temporary living nest is produced, inside which the queen 

 and brood can be protected and in and out of which the other 

 workers will be seen passing. The temporary nature of most 

 of these colonies appears to be the inescapable result of their 

 mode of life. Ants which occur in such large numbers and 

 which live exclusively by hunting soon denude any one area 

 of food and have to move on. There are many accounts 

 not only of the ordinary predatory raids but of the shifting of 

 the whole colony when all the brood is carried to a new site. 



Some idea of the physiological background to the restless 

 activity of these ants has been obtained recently in America, 



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