THE MASON BEES 127 



seemed to be an easy task for her until the hole 

 was over "bee deep." But after the hole grew 

 deeper our excavator found the task so difficult 

 that she had to adopt new tactics. So now she 

 began throwing the earth beneath her and out 

 of the hole with her rear legs. One could not 

 help comparing her motions with those of a dog 

 digging an animal from its hole. To keep the 

 tube well rounded I could see her constantly- 

 turning her body this way and that, as she 

 worked now on one side and then on the other. 

 The edges of the burrow and of the cylindrical 

 tubular case itself were smoothed and made firm 

 by the constant application of wax, secreted 

 from glands on her own body, and squirting on 

 of saliva. When the tube was completed, she 

 built about the orifice a small circular collar of 

 mortar which she compounded of particles of 

 earth, minute pieces of gravel, and her own 

 saliva, so that the hollow, cistern-like cell 

 looked very much like an old-fashioned well 

 with its round curb, or coaming, about the 

 opening. Ten minutes after it was made, I was 

 amazed to find that this cement had set so hard 

 and had become so rigid that, although I did 



