58 
Psyche 
[April 
several times, finally flying to a tree twenty feet distant. The 
stone was then replaced on the true nest. The wasp returned, 
still bearing her prey, tried the false nest as before, but almost 
immediately went to the right nest and entered. 
This wasp was captured for identification as she was about 
to complete her nest at 1 o’clock (June 21). 
Nest No. 7. Another Ancistrocerus capra was discovered 
constructing her nest on the same day at 5 P. M. Two hours 
later she had made a basal wall of mud, deposited an egg and was 
resting in the tube. 
During the mud-carrying operations of this wasp, I re- 
moved the stone which marked her nest and placed it six inches 
to one side. Returning, she flew directly for a point beneath the 
removed stone, discovered her error and flew along the wall in a 
horizontal direction, pausing before another nesting block, 
similarly located on an adjacent window ledge and similarly 
marked by a small stone. She hovered in front of this empty 
nest, still holding the lump of mud she was carrying, then sud- 
denly made a swift flight perpendicularly from the building? 
turned and made a bee line for her true nest, which she found 
without delay. The stone was not immediately replaced, but 
the wasp on subsequent trips entered her nest without hesita- 
tion, approaching it, however, in a perpendicular direction, 
instead of obliquely as she had done before her landmark had 
been misplaced. When the stone was replaced she continued to 
enter the nest without confusion. 
The second day of this wasp’s activities was extremely hot 
and humid. I had always believed that such a day would be 
particularly conducive to work with the wasps, and was surprised 
to find that this individual responded to the heat in much the 
same manner as her observer, for she remained in her nest the 
greater part of the day and brought in only three caterpillars? 
one in the early morning and two in the late afternoon. The 
following day (June 23) heavy clouds kept off the heat of the sun 
during the morning so that by ten o’clock four caterpillars had 
been stored. A half hour later the rim of the closing partition of 
