214 THE SOLITARY WASPS. 



finding it. As an example of this kind of trouble we give a dia- 

 gram (PL Xn., fig. 5), of the course followed by an individual 

 of fuscipennis, after she had finished her nest, in trying to find 

 her spider and, in bringing it home. This and the other similar 

 diagrams that are given, are reductions of large tracings that 

 were made on the spot. Although not absolutely correct they 

 are exact enough for all practical purposes. Whenever there 

 is an error it is necessarily in the direction of making the path 

 pursued by the wasp appear shorter and less complex than it 

 really was. The individual in question had placed her spider 

 on a cucumber vine not far from the ground. It was not hid- 

 den by leaves but was fully exposed to view. The nest was 

 only eight inches away but when it was finished and the wasp 

 went to bring the spider, she found it only after a search of 

 three minutes, and then when she went back to the nest she at 

 first passed to one side and went some inches beyond and had to 

 retrace her steps. 



We watched ten different individuals of this species and every 

 one of them had trouble in remembering the path between the 

 nest and the spider. Once we caught one that had just hung up 

 her spider, and released her, almost immediately, on the same 

 spot. She hunted about in the wildest way for fifteen minutes, 

 going further and further away, and would never have found 

 her treasure if we had not helped her. Such an amount of run- 

 ning and flying, here, there, and everywhere, would be incom- 

 prehensible in an animal endowed with an innate sense of direc- 

 tion, and we fear that the wasps must surrender to the bees or 

 the cats all claim to such distinction. Certainly we have discov- 

 ered no trace of it in the forty-five species that we have studied. 



The best evidence that wasps depend upon a knowledge of 

 the place in returning to their nests, is given by the pains that 

 they take to acquire that knowledge. When Sphex ichneumo- 

 nea was ready to dig her nest she had great difficulty in find- 

 ing a place that suited her. Many a spot was merely looked at 

 and passed by, while others, that seemed more attractive, were 

 left after they had been excavated for a little way. At last, 



