Bramble-bees and Others 



ready collected. If the width of the tube does 

 not admit of this operation, if the insect is 

 obliged to go out and then to come in again 

 backwards in order to place itself in a favour- 

 able posture for the discharge of the pollen, 

 the reed is too narrow and the Osmia is rather 

 reluctant to accept it. The middle-sized reeds 

 and a fortiori the large ones leave the vic- 

 tualler entire liberty of action; but the former 

 do not exceed the width of a cell, a width 

 agreeing with the bulk of the future cocoon, 

 whereas the latter, with their excessive dia- 

 meter, require more than one chamber on the 

 same floor. 



When free to choose, the Osmia settles by 

 preference in the small reeds. Here, the work 

 of building is reduced to its simplest express- 

 ion and consists in dividing the tube by means 

 of earthen partitions into a straight row of 

 cells. Against the partition forming the back- 

 wall of the preceding cell, the mother places 

 first a heap of honey and pollen; next, when 

 the portion is seen to be enough, she lays an 

 egg in the centre of it. Then and then only 

 she resumes her plasterer's work and marks 

 out the length of the new cell with a mud par- 

 tition. This partition in its turn serves as the 



214 



