THE OSMLE 257 



If the gallery is at all long, this crawling backwards be- 

 comes troublesome after a time; and the Osmia soon 

 abandons a passage that is too small to allow of free 

 movement. I have said that the narrow tubes of my 

 apparatus are, for the most part, only very incompletely 

 colonized. The Bee, after lodging a small number of 

 males in them, hastens to leave them. In the wide front 

 gallery she can stay where she is and still be able to turn 

 round easily for her different manipulations; she will 

 avoid those two long journeys backwards, which are so 

 exhausting and so bad for her wings. 



Another reason no doubt prompts her not to make too 

 great a use of the narrow passage, in which she would 

 establish males, followed by females in the part where 

 the gallery widens. The males have to leave their cells 

 a couple of weeks or more before the females. If they 

 occupy the back of the house they will die prisoners or 

 else they will overturn everything on their way out. This 

 risk is avoided by the order which the Osmia adopts. 



In my tubes, with their unusual arrangement, the 

 mother might well find the dilemma perplexing: there 

 is the narrowness of the space at her disposal and there 

 is the emergence later on. In the narrow tubes, the 

 width is insufficient for the females ; on the other hand, 

 if she lodges males there, they are liable to perish, since 

 they will be prevented from issuing at the proper mo- 

 ment. This would perhaps explain the mother's hesi- 

 tation and her obstinacy in settling females in some of 

 my apparatus which looked as if they could suit none 

 but males. 



