The Eumenes 



by friction under water. Some are of lime- 

 stone, others of flinty material. The 

 favourite stones, when the neighbourhood 

 of the nest permits, are smooth, semitrans- 

 parent little lumps of quartz. These are 

 selected with minute care. The insect 

 weighs them, so to say, measures them with 

 the compass of its mandibles and does not 

 accept them until after making sure that 

 they possess the requisite qualities of size 

 and hardness. 



A circular fence, we were saying, is be- 

 gun on the bare rock. Before the mortar 

 sets, which does not take long, the mason, 

 as the work advances, sticks a few stones 

 into the soft mass. She dabs them half- 

 way into the cement, so as to leave them 

 jutting out to a large extent, without pene- 

 trating to the inside, where the wall must 

 remain smooth for the sake of the larva's 

 comfort. If necessary, she adds a little 

 plaster, to tone down any inner excrescences. 

 The solidly-embedded stonework alternates 

 with the pure mortarwork, of which each 

 fresh course receives its facing of tiny en- 

 crusted pebbles. As the edifice is raised, 

 the builder slopes the construction a little 

 towards the centre and fashions the curve 

 which will give the spherical shape. We 

 7 



