HYMENOPTERA. 



365 



galleries in decayed wood, and builds in them cells placed one over 

 the other a work often occupying many weeks. She then furnishes 

 the bottom of the cell with pollen mixed up with honey, lays an egg 

 jn the middle of this paste, and closes the cell by a ceiling of sawdust 

 agglutinated with saliva. On this ceiling she establishes a new cell, 

 and so on, right up to the orifice, which she closes in the same 



Interior of the Nest of the Mason Bee. 



manner. Reaumur is astonished, with reason, at the admirable in- 

 stinct which makes this provident mother determine the exact quantity 

 of nourishment which will be necessary for its larva. When this 

 has absorbed all its provisions, it alone quite fills up its cell, and 

 changes into a pupa. It is worthy of remark, that the head of the 

 young is always turned downwards, in such a way that it is by the 

 bottom of its cell that it comes out. The bottom of the first is very- 

 near the surface of the wood, so that the insect it encloses has only a 

 thin layer of wood to pierce through in order to set itself free. Each 

 one of those which are born next has only to pierce the floor of it* 



