THE BEMBICENE WASPS 19 



old place should have been abandoned, or that the new was 

 in any way its superior. We watched one wasp begin 

 one hole after another. Frequently others would fly down 

 and alight with a thump beside her and violently bump her 

 (but without actually seizing her). Thus disturbed, each 

 time she arose on the wing at once and went off a short 

 distance a few inches or a few feet and began a new 

 hole. After eight such interrupted attempts, she seemed 

 to learn not to mind the intruders further, and continued 

 to work on this hole while twenty-four others, one by one, 

 flew down and butted her in this fashion, but finally she 

 gave up this one also after it was well begun. After this 

 we lost sight of her. 



This case which we have followed in detail was no ex- 

 ception, but only a sample of the conduct of many of the 

 swarm ; some continued work upon their first or second hole, 

 but all who attempted to dig were annoyed thus by the in- 

 trusion of others. The significance of this strange form 

 of attention we have never been able to determine with 

 certainty; but we have come to suspect that the intrud- 

 ers, seeing the owner of the burrow digging, suspected 

 that she was entering her nest with a fly and pounced upon 

 her to rob her of it. The Peckhams find the same habit in 

 B. spinolae. 



On two different occasions, when some of the B. nubili- 

 pennis were in a bumping mood, one swooped down upon 

 a Sphex pictipennis that was carrying her caterpillar. A 

 short struggle ensued, but both times when B. nubilipennis 

 flew away, 6\ pictipennis resumed her walk. On one occa- 

 sion a B. nubilipennis dropped a fly which she was carrying 

 to her burrow, and, almost before it struck the ground, a 

 sister wasp swooped down upon it and carried it away. 



We do not know how long a time is required in which 

 to dig the burrow, but we have one record of a nest that 



