Field Studies of the Non-Social Wasps 453 
placed the nest, but before doing so I removed five 
spiders from the cell which she was engaged in filling. 
She returned, still with the green spider which she car- 
ried when first she found her nest gone. She came back 
and hovered about on the nest very nervously for some 
minutes and entered the cell five or six times, seeming 
greatly excited and puzzled; she re-examined the whole 
nest again and again and re-entered the cell many times, 
and finally after thus hesitating for about forty minutes 
she soared away with an indignant buzz without even 
depositing her new prey. 
While she was gone I removed six spiders from an- 
other cell of her own nest (this cell was at the back of 
the nest, against the wall, so one side was open, but 
when the nest was returned to its position against the 
wall, no mutilation was apparent to confuse the owner) 
and placed them in the new cell. She returned and set 
about promptly to remove these six spiders, which were 
probably her own, and either dropped them one by one 
after a flight of a few inches from the nest or carried 
them quite outside the barn. 
Apparently she had had enough of this cell, for after 
a few minutes she flew in with a pellet of mud and sealed 
it up, stark empty. 
Exp. IV. A Sceliphron mother was busily engaged 
in stocking her new cell. I plundered the nest of a mud 
wasp near by and placed six spiders from it in the new 
cell. The owner returned with a spider of her own, 
placed it in the cell on top of the stolen booty, pushed 
the whole in with her head and rammed it down about 
six times as though it were all her own, then flew out, 
returning almost at once with a pellet of mud with which 
she sealed the cell, and reinforced it with five more such 
