The Return to the Nest 3 1 1 



basket or a box. Locality, relative position : 

 everything is unknown to them ; and yet they 

 find their way. They therefore have something 

 better than mere memory as a guide : they have 

 a special faculty, a sort of topographical sense 

 of which we cannot possibly form an idea, having 

 nothing similar ourselves. 



I will show by experiment how subtle and 

 precise this faculty is within its narrow 'pro- 

 vince, and also how obtuse and dull it becomes 

 when driven to depart from the usual conditions 

 in which it acts. This is the invariable anti- 

 thesis of instinct. 



A Bembex, actively engaged in feeding her 

 larva, leaves the burrow. She will return pre- 

 sently with the produce of the chase. The en- 

 trance is carefully stopped up with sand, which 

 the insect has swept there backwards before 

 going away ; there is nothing to distinguish it 

 from other points of the sandy surface ; but this 

 does not trouble the Wasp, who finds her door 

 with a skill which I have already emphasized. 

 Let us devise some insidious plot and change the 

 conditions of the locality in order to perplex the 

 insect. I cover the entrance with a flat stone, 

 the size of my hand. The Wasp soon arrives. 

 The great change effected on her threshold 

 during her absence appears to cause her not the 

 slightest hesitation ; at least, the Bembex at 



