SENSE OF DIRECTION 



ledge of the place in returning to their nests is given by 

 the pains they take to acquire that knowledge. When 

 Sphex ichneumonea was ready to dig her nest, she had 

 great difficulty in finding 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, the nest dug, 

 she was ready to go out and seek for her store of pro- 

 visions; and now came a most thorough and systematic 

 study of the surroundings. The nests that had been 

 partly made and then deserted had been left without 

 any circHng. Evidently she was conscious of the differ- 

 ence and meant, now, to take all necessary precautions 

 against losing her way. She flew in and out among the 

 plants, first in narrow circles near the surface of the 

 ground, and now in wider and wider ones as she rose 

 higher in the air, until at last she took a straight line and 

 disappeared in the distance. Very often, after one 

 thorough study of the topography of her home has been 

 made, a wasp goes away a second time with much less 

 circling or with none at all. 



If the examination of the objects about the nest 

 makes no impression upon the wasp, or if it is not re- 

 membered, she ought not to be inconvenienced nor 

 thrown off her track when weeds and stones are removed 



285 



