1922] Taylor — Biology of Wasps of Genus Ancistrocerus 57 
finished the wasp backed out of the tube, turned about and 
backed in presumably to oviposit, but strangely no egg was laid 
until half an hour later (5:30 P. M.). At six o’clock she brought 
in a caterpillar and suspended operations, remaining asleep in 
the cell all night. 
During the building of the partition described above, I re- 
moved a small stone which had been resting on the nesting block 
and placed it a few inches to one side of the nest while the wasp 
was away. On her return, instead of flying directly to the en- 
trance as she had been doing, she made for a position just beneath 
the misplaced stone. Discovering her mistake, she soon found 
her nest by flying about at a few inches from the wall. A little 
later, while examining the tube during the wasp’s absence, I 
placed the entrance block on the window sill at a short distance 
from its right position. The wasp returned and entered the hole 
in the entrance block. Finding nothing behind it, she retreated 
for some distance, and the nest meanwhile having been replaced, 
she then entered without hesitation. This would seem to in- 
dicate that certain objects, such as the stone, serve as guides to 
the wasp, but this and further observations show that the wasp 
is not helpless when such guides are removed, since after once 
finding her nest in the absence of the stone she apparently made 
use of other means to locate her nest. 
June 21 at 9:15 A. M. wasp No. 6 was carrying in mud. 
This she deposited and went off again returning with a drop of 
water shining at her mouth. She was apparently just finishing 
a partition, for she appeared at the entrance, came out and 
backed in, remaining within for three minutes to lay an egg. 
Oviposition finished, she appeared at the entrance and after ex- 
citedly waving her antennae, flew off. 
At this time I made a further test of her ability to locate her 
nest by placing a similar nesting block about five inches away 
from the original and marking it with the stone which had for- 
merly served as a guide. At 10:00 A. M. the wasp came back, 
bearing a large green caterpillar; she flew directly to the wrong 
nest, but did not enter, retreating from it and approaching it 
