One day we saw a quinquenotatus finish her nest and go after her spider. She was absent for some time, and when an ant passed by, dragging a paralyzed strix that had evidently been stolen from some wasp, we thought that the one we were watching had been robbed, and rescuing the spider, placed it in the doorway of the nest. We had judged wrongly, for a moment later our wasp came back bringing her own spider, and dropping it near by, ran to look at her nest. She was disturbed at finding the way blocked, and dug out a little earth to one side of the strix. Then she flew to some holes in the ground not far away and dug a little, first in one and then in the other. After this she took a look at her spider, and then went back and dug a little more at her own nest. Finally she seized the impeding strix by a leg, dragged it out of the way and paid no further attention to it, storing her own spider and departing, although the one she had rejected might have saved a hunting expedition. At another time we saw two wasps digging their nests two or three feet apart. One of them finished before the other, and being unable to find her own spider (probably it had been carried away by the ants), she seized that of her neighbor and bore it away. The rightful owner saw from a distance what was happening, and ran to the rescue. A violent scrimmage ensued, the two wasps clinching and rolling over and over together. The robber escaped and made off, but was followed and caught again. She fought so well for her ill–gotten treasure, however, that she finally conquered the other and hurried off with her prize. She showed by her manner that she felt the need of haste, for instead of laying the spider down and looking at the nest, she dragged it directly in, as though she feared another attack. This was the first time that we had ever seen these wasps fighting over their prey, and we were surprised to find that they would take spiders which they had not captured themselves, since when we had tried to exchange with them they had refused to carry out our scheme. This was clearly an intelligent act, and could not be an affair of instinct. Once again we witnessed a similar struggle. One of these wasps was laboriously dragging her strix up a steep hillside, when a much bigger one of the same species descended upon her and seized the spider. She was loath to give it up, and they both pulled until it seemed as though the poor creature would be dismembered. The highway robber came off victorious, and after flying to a distance hung the spider up while she finished a partly made nest, and then stored it away. It may be said in extenuation of her conduct that since she had a nest started she had probably been robbed herself, and therefore felt that she was entitled to a spider.