THE KEYSTONE 



an inch across and not quite so much in height. It is 

 attached by its wide base to the rock, and opens towards the 

 top by a neck the rim of which is gracefully curved out- 

 wards. In building this nest, Eumenes makes use of saliva 

 mixed with very dry dust collected from dusty roads, 

 combined with tiny fragments of stone, especially quartz, 

 and sometimes with little shells. 



Fabre observed that the builder, having selected a suitable 

 spot, first raises a little circular wall about an eighth of an 

 inch in thickness ; then before the cement has had time to 

 become hard which it does very soon she embeds a few 

 stones in the soft mass as the work proceeds. She half 

 buries them in the cement in such a manner that they project 

 considerably from the outer wall, but do not penetrate to the 

 interior of the cell, which has to be kept smooth for the 

 comfort of the grub. Any inside irregularities are smoothed 

 over when need be with the aid of a little cement. The 

 stones are solidly set, a layer of mortar is spread over them, 

 then another course of stones is laid, and so on alternately. 

 As the work proceeds the walls are gradually made to slope 

 towards the centre so that the building is given just that 

 curvature which results in the more or less spherical shape 

 mentioned above. When we build a vaulted chamber we 

 use wooden arches to support the masonry until the keystone 

 which makes all secure is placed in position ; but the Eumenes 

 is more daring than we are, for she erects a cupola in space 

 without any scaffolding whatever to aid her. At the summit 

 a round hole is fashioned, leading into a mouth made of pure 

 cement, the edges of which are 'lipped' outwards. It 

 reminds one of the gracefully curved neck of an Etruscan 

 vase. When the cell has been provisioned and an egg has 

 been deposited in it, this neck is closed up with a plug of 

 cement and in the cement a little stone is set one only, 



143 



