The Mason-bees 



raised when a mere paper barrier is in ques- 

 tion. 



In addition to the cells made out of bits of 

 reed, I put under the bell-glass, at the same 

 time, two nests which are intact and still rest- 

 ing on their pebbles. To one of them I have 

 attached a sheet of brown paper pressed close 

 against the mortar dome. In order to come 

 out, the insect will have to pierce first the 

 dome and then the paper, which follows with- 

 out any intervening space. Over the other, 

 I have placed a little brown-paper cone, 

 gummed to the pebble. There is here, there- 

 fore, as in the first case, a double wall — a clay- 

 partition and a paper partition — with this dif- 

 ference, that the two walls do not come im- 

 mediately after each other, but are separated 

 by an empty space of about a centimetre at 

 the bottom, increasing as the cone rises. 



The results of these two experiments are 

 quite different. The Bees in the nest to which 

 a sheet of paper was tightly stuck, come out 

 by piercing the two enclosures, of which the 

 outer wall, the paper wrapper, is perforated 

 with a very clean round hole, as we have al- 

 ready seen in the reed cells closed with a lid 

 of the same material. We thug become 



