Bramble-Dwellers 



avoidable error, belong to females. I pack 

 them in tubes, sometimes varying their posi- 

 tion in every way, sometimes giving them all 

 a like arrangement. It does not matter 

 whether the whole series comes from one 

 and the same bramble-stump or from several : 

 we are free to choose where we please; the 

 result will not be altered. 



The first time that I prepared one of these 

 horizontal tubes open at both ends, I was 

 greatly struck by what happened. The series 

 consisted of ten cocoons. It was divided into 

 two equal batches. The five on the left went 

 out on the left, the five on the right went out 

 on the right, reversing, when necessary, their 

 original direction in the cell. It was very re- 

 markable from the point of view of sym- 

 metry; moreover, it was a very unlikely ar- 

 rangement among the total number of possi- 

 ble arrangements, as mathematics will show 

 us. 



Let us take n to represent the number of 

 Osmias. Each of them, once gravity ceases 

 to interfere and leaves the insect indifferent to 

 either end of the tube, is capable of two posi- 

 tions according as she chooses the exit on the 

 right or on the left. With each of the two 



43 



