ants' habitations 



137 



number of subterranean chambers, often under the shelter of a 



stone, and connected by galleries. It is of course very difficult to 



trace exactly the details of such a work, because when excavations 



are made for the purposes «of examination, the construction becomes 



destroyed ; it is known, however, that some of these systems 



extend to a considerable depth in the earth, it is said to as much 



as nine feet, and it is thought the object of this is to have access 



to sufficiently moist earth, for ants are most sensitive to variations 



in the amount of moisture ; 



a quite dry atmosphere is in 



the case of many species very 



speedily fatal. This system 



of underground labyrinths 



is sometimes accompanied by 



above-ground buildings con- 

 es o 



sisting of earth more or less 

 firmly cemented together by 

 the ants ; this sort of dwell- 

 ing is most frequently adopted Fig. 58.— Portion of combined nest of For- 



When the soil in which the micafusca and Solenopsis fugox. (After 



. . Forel.) X f . /,/', Chambers of i^o?-?)«'ca, 



nests are placed is sandy \ it recognisable by the coarser shading ; 



is probable that the earth is '' ''> chambers of the Solenopsis (with 



■^ nner shading) ; s , openmg in one or the 



in such cases fastened together chambers, the entrance to one of the 



by means of a cement pro- galleries that connects the chambers of the 



•^ ■•■ bolenoj^sis ; u; walls lormiug the lounda- 



duced by the salivary glands tions of the nest and the limits of the 



of the ants, but this has not ^ ^'^™ ^^^"^ 



been determined with certainty ; vaulted galleries or tunnels of 

 this kind are constructed by many species of ants in order to 

 enable them to approach desired objects. 



In South America Campoiiotus rufi'pes and other species that 

 habitually dwell in stumps, in certain districts where they are 

 liable to inundations, build also nests of a different natm-e on 

 trees for refuge during the floods. In Europe, a little robber-ant, 

 Solenopsis fugax, constructs its dwelling in combination with that 

 of Formica fusca (Fig. 58), in such a manner that its chambers 

 cannot, on account of the small size of the orifices, be entered by 

 the much larger Formica. Hence the robber obtains an easy 

 living at the expense of the larger species. The Sauba or Sauva 

 ants of South America (the genus Atta of some, Oecodoma of 

 other authors) appear to be most proficient in the art of sub- 



