112 ANIMAL INTELLiaENCE. 



III. Black workers, guards, and purveyors ; surround the 

 nest as guards or sentinels, in a manner presently 

 to be described, and also forage for the food required 

 for I. They are much larger and stronger insects 

 than either I. or II., and are provided with very 

 formidable mandibles. 



The nest is placed in sandy soil in the neighbourhood 

 of shrubs and flowers, is a perfect square, and occupies 

 about four or five square feet of ground, the surface of 

 which is kept almost unbroken. But the boundaries of 

 the nest are rendered conspicuous by the guard of black 

 workers (III.), which continuously parade round three of 

 its sides in a close double line of defence, moving in 

 opposite directions. In the accompanying diagram this 

 sentry path is represented by the thick black lines. These 

 always face the same points of the compass, and the 

 direction in which the sentries march is one column from 

 south-west to south-east, and the other column from south- 

 east to south-west — each column, however, moving in 

 regular order round three sides of a square. The southern 

 side of the encampment is left unguarded; but if any 

 enemy approaches on this or any other side, a number of 

 the guards leave their stations, and sally forth to face the 

 foe — raising themselves on their hind tarsi on meeting the 

 enemy, and moving their large mandibles in defiance. 

 Spiders, wasps, beetles, and other insects, if they venture 

 too near the nest, are torn to pieces by the guard in a 

 most merciless manner, and the dead body of the van- 

 quished is speedily removed from the neighbourhood of the 

 nest — the guard then marching back to resume their 

 places in the line of defence, their object in destroying 

 other insects being the defence of their encampment, and 

 not the obtaining of food. 



The object of leaving the southern side of the square 

 encampment open is as follows. While some of the black 

 workers are engaged on duty as guard, another and larger 

 division are engaged on duty as purveyors. These enter 

 and leave the quadrangle by its open or southern side 

 along the dotted line marked a to the central point c. 

 The incoming line is composed of individuals each bearing 



