1922] Taylor — Biology of Was'ps 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 antennse, 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 



