112 Chapter III. 



guinea selects for its nest a more hidden place than a 

 stronger one does. This is especially the case, if there 

 are hostile ant species in the neighborhood, liable to 

 pay them a visit at any time. Thus colony i66 of my 

 statistical map of Exaten, being harassed by neigh- 

 boring pratensis, had at last hidden itself so well in 

 the earth, that I was obliged to spend a considerable 

 time before finding it. I myself have often enough 

 been vexed to see that colonies of the same sanguinea, 

 on being disturbed even by the hand of man, emigrate 

 and seek elsewhere a new place of settlement. Some- 

 times even a clod of heather placed on their nests will 

 cause weaker colonies to emigrate. This is all the 

 more strange, since our sanguinea is very fond of 

 using such clods as a roofing for her nests. Other 

 colonies, indeed, did not emigrate on account of my 

 repeated visits, but tried to retire farther into the 

 interior. A striking instance of this kind was offered 

 by colony No. 36, which was of moderate dimensions. 

 Originally the exterior of the nest looked like any 

 common earth-nest of the same numerical strength. 

 The clod which I had placed on it was used as a roof 

 and was covered by a heap of dry heather leaves. I 

 often visited the nest and each time I lifted the clod 

 to have a view of the interior of the building. In con- 

 sequence the ants blocked up the former entrances; 

 they dug new ones at a greater distance from the 

 nest, and came to the surface much more rarely. Even 

 the small heap of materials gathered from plants 

 gradually disappeared from the top of their nest. 

 After a time it was blown or washed away, nor did 

 the ants renew it. It was evidently instinct that led 



