198 THE INDUSTRIES OF ANIMALS. 



methods transmitted to him by his ancestors, accord- 

 ing to his own experience and his own judgment. 



Built dwellings. — The built dwelling, the expression 

 of the highest civilisation, still remains to be studied. 

 Man has only known how to construct this kind of 

 shelter at a comparatively late period in his evolution; 

 and among animals we do not find it widely spread, 

 much less so, certainly, than the two foregoing methods, 

 especially the first. The difficulty of this work is 

 greater, and it only arrives at considerable develop- 

 ment among very sociable species, since the united 

 efforts of a great number of individuals are needed to 

 carry it on. 



There are, however, masons who operate separately; 

 but their constructions are rudimentary. The char- 

 acteristic of all these works is that they are manu- 

 factured with some substance to which the animal 

 gives a determined form while it is still soft, and that 

 in drying it preserves this form and acquires solidity. 

 The matter most usually employed is softened and 

 tempered earth — mortar ; but there are animals who 

 use with success more delicate bodies. Two examples 

 will suffice to indicate the nature of these exceptions : 

 the labours of Wasps and those of certain Swallows. 



Paper nests. — Certain Wasps, by the material of 

 their dwellings, approach the Japanese ; they build 

 with paper. This paper or cardboard is very strong 

 and supplies a solid support; moreover, being a bad 

 conductor of heat, it contributes to maintain an 

 equable temperature within the nest. The construc- 

 tions of these insects, though they do not exhibit the 

 geometric arrangement of those of Bees, are not less 

 interesting. The paper which they employ is manu- 

 factured on the spot, as the walls of the cells 



