DWELLINGS. 221 



it became a question of decreasing the resistance at 

 the base. The ant gnawed a little at this spot ; the 

 desired result was attained, and the whole length of 

 the leaf became bent over the building in course of 

 construction. To prevent it bending back, and to 

 ensure its remaining adherent to the roof, the worker 

 returned to the plant and placed earth between the 

 sheath and the stalk. This time all difficulties were 

 surmounted, and there was a solid scaffolding to 

 support the materials for the roof 



Among the Lasius niger the independence of the 

 workers is perhaps still greater ; no doubt they do 

 their best to concert their efforts, but they do not 

 succeed so well as if an inevitable instinct impelled 

 them. Notwithstanding the irregularities of the con- 

 struction, it is possible to recognise in it a whole 

 formed of hollowed, concentric half-spheres ; they 

 have been added one after the other to the surface to 

 increase the dwelling. The interval between these 

 clay spheres constitutes a storey, cut up by the par- 

 titions which divide it into chambers and communi- 

 cating galleries ; the roofs of the largest halls are 

 supported by numerous pillars. (Fig. 40.) 



These ants, as Huber has shown, are highly 

 accomplished in the art of constructing a cupola 

 When they wish to increase their nest by a new 

 layer, they take advantage of the first wet day, the 

 rain serving to agglutinate and unite the materials. 

 They operate in almost the same way as the Formica 

 fusca, though exhibiting more skill and resource as 

 architects ; they know better how to calculate before- 

 hand the number of pillars required in a hall of a 

 determined size. As soon as the rain has given the 

 signal for work, they spread themselves abroad and 



