Field Studies of the Non-Social Wasps 455 
she walked over her nest and deposited the mud on the 
outside to reinforce it; she did not enter the cell, and 
I did not see her even look inside, but when she again 
came she used the load of mud to close the cell, then 
another and another until the seal was firm, just as 
though all were normal. Whether she detected the 
ample supply of spiders and closed the cell on that ac- 
count, or whether she would have sealed it empty, had 
I not filled it for her, I could not determine, 
Exp. VIII. A mud-dauber’s cell was finished and 
quite ready for use, but the larder was not yet stocked, 
so I filled it with provisions borrowed from another nest. 
The mother wasp returned with a fresh spider, started 
to enter the nest but retreated and flew out of the win- 
dow, taking her burden with her. She returned empty- 
handed and carried out the substitutes one by one. After 
the cell had been empty for a half-hour, I again placed 
eleven spiders in it. The next morning when I arrived 
to examine this cell I found it had again been emptied. 
Exp. IX. A Sceliphron mother was carrying in spi- 
ders to fill the twelfth cell of a handsome nest, but had 
not gone far with the work when I added fourteen from 
the nest of another of the same species. The wasp re- 
turned and at once emptied the cell of my spiders and 
her own as well, quietly stood guard over the cell for 
a quarter of an hour with an air of indecision, and then 
flew away and was not seen again. 
Exp. X. <A one-celled Sceliphron nest was built under 
a piece of bark on a log beam in the old barn. I care- 
fully removed this bark, filled the cell with borrowed 
spiders and replaced it so it looked, to my eye, exactly 
as it had before. When the wasp returned, she had 
great difficulty in finding the nest. After locating it, 
she paused only a moment and dashed away, and, re- 
