ABILITY OF MUD-DAUBER TO RECOGNIZE OWN PREY 245 



crammed into the cell with the others and departed. After ten 

 minutes, however, she came buzzing back as if possessed of a 

 new idea, and commenced to empty the cell. First she took 

 out her own fine new one and threw it away, and returned re- 

 peatedly until the cell was again empty. She then remained on 

 the nest, holding watch for thirty minutes, as if resolutely wait- 

 ing to catch the hoodoo. When she left I expected her to refill 

 the nest with spiders of her own capture, but instead she brought 

 a load of mud and, to my amazement, spread it in a thin 

 layer on the inside of the cell, as though the very walls were 

 polluted, or else all of the trouble were due to its inadequacy. 

 So, for the first time, I saw a wasp adding mud to the inside 

 walls of a cell after she had once deemed it finished. . 



The next day, August 17, at three p. m., she was still occa- 

 sionally coming to the cell with an air of angry suspicion and 

 uncertainty, but otherwise it was in the same empty condition 

 that I had left it. Unfortunately I was obliged to leave on the 

 evening train, so I never knew what she finally decided to do. 



£#£.12 . At six o'clock one August evening I filled a new 

 one-celled Pelopoeus nest with spiders from another nest during 

 the absence of its owner. I was called away and could observe 

 it no further until the next day, August 17, when I found the 

 cell sealed. I opened it and found that my intruders were gone 

 and in their stead were two other spiders. The mother had 

 evidently begun to fill the cell after having thrown out my 

 spiders but had stopped with only two and sealed the cell with- 

 out having even deposited her egg. 



Exp. 13. A certain nest of a Pelopoeus was almost com- 

 pleted when I filled it with spiders from another nest. The 

 proprietress returned with another load of mud to add another 

 ring. When she saw the spiders she withdrew her head with 

 a start, as though greatly shocked. Again she inquiringly put 

 in her head, with a like result. She then went away in bewilder- 

 ment and returned six times, but each time sought the nest at 

 a spot two feet distant. Sometimes she would walk toward the 

 nest, but always with the manner of one seeking for something 

 lost. 



After three days the cell was still in the same condition as I 

 had left it; the wasp never finished it. I think that she firmly 



