XX 



MASON BEES 281 



she can find dry earth, rich in small gravel, near the 

 boulder chosen as the basis of her nest, she is con- 

 tented. She may either make quite a new nest in a 

 spot hitherto unoccupied, or over the cells of an old 

 one, after repairing them. Let us consider the first 

 case. 



After choosing a boulder, she comes with a pellet 

 of mortar in her mandibles, and arranges it in a ring 

 on the surface of the pebble. The forefeet, and above 

 all the mandibles, which are her most important 

 tools, work the material, which is kept plastic by 

 the gradually disgorged saliva. To consolidate the 

 unbaked clay, angular pieces of gravel, as large as 

 a small bean, are worked in singly on the outside 

 of the still soft mass. This is the foundation of the 

 edifice. Other layers are added until the cell has 

 the required height of three or four centimetres. 

 The masonry is formed by stones laid on one another 

 and cemented with lime, and can stand comparison 

 with our own. True, to economise labour and mortar, 

 the bee uses coarse materials, — large bits of gravel, 

 which in her case answer to hewn blocks. They are 

 chosen singly — very hard ones, almost always with 

 angles which, fitted together, give mutual support, 

 and add solidity to the whole. Layers of mortar, 

 sparingly used, hold them together. The outside of 

 the cell thus assumes the look of a piece of rustic 

 architecture, in which stones project with their natural 

 inequalities ; but over the inside, which requires a 

 smoother surface in order not to wound the tender 

 skin of the larva, is spread a wash of pure mortar — 

 artlessly, however, as if by broad sweeps of a trowel ; 

 and when it has eaten up its honey paste, the grub ; 



