Reflexes, Instincts, and Intelligence 649 



to come, is this: Afier withdrawing the prey of S. albisecta several times 

 from the mouth of the hole, and obliging her to fetch it back, I profited by 

 her descent to the bottom of her den to seize and put the prey where she 

 could not find it. She came up, sought about for a long time, and, when 

 quite convinced that it was not to be found, went down again. A few mo- 

 ments later she reappeared. Was it to return to the chase? Not the least 

 in the world ; she began to close the hole, and with no temporary cover, such 

 as a small flat stone to mark the orifice, but with a solid mass of carefully 

 collected dust and gravel swept into the passage until it was quite filled. S. 

 albisecta makes only a single cell at the bottom of her well, and puts in but one 

 victim. This one specimen had been caught and dragged to the edge of the 

 1 ole, and if it was not stored, that was my fault, not her's. The Sphex 

 worked by an inflexible rule, and according to that rule she completed the 

 work by stopping up the hole even if empty. Here we have an exact repe- 

 tition of the useless labor of S. occiianica, whose dwelling I rifled. 



"Fourth experiment. It is almost impossible to be certain whether S. 

 flavipennis, which makes several cells at the bottom of the same passage, 

 and heaps several grasshoppers in each, commits the same irrational mis- 

 takes when accidentally disturbed. A cell may be closed, although empty 

 or imperfectly stored, and yet the Sphex will return to the same burrow to 

 make others. Yet I have reason to believe that this Sphex is subject to the 

 same aberrations as her two relations. The facts on which I base my belief 

 are these: When the work is completed, there are generally four grass- 

 hoppers in each cell, but it is not uncommon to find three or only two. Four 

 appears to me the usual number first, because it is the most frequent, and 

 secondly, when I have brought up young larvae dug up when eating their 

 first grasshopper, I found that all, even those provided with only two or three, 

 easily finished those offered, up to four, but after that they hardly touched 

 the fifth ration. If four grasshoppers are required by the larva to develop 

 fully, why is it sometimes provided with only three or even only two ? Why 

 this immense difference in the amount of food? It cannot be from any 

 difference in the joints served up, since all are unmistakably of the same 

 size, but must come from losing prey on the road. In fact, one finds at the 

 foot of the slopes whose upper parts are occupied by Sphegidas, grasshop- 

 pers killed, and then lost down the incline, when, for some reason or other, 

 the Sphex has momentarily left them. These grasshoppers become the prey 

 c f ants and flies, and the Sphex who finds them takes good care not to pick 

 them up, as they would take enemies into the burrow. 



"These facts seem to demonstrate that if S. flavipennis can compute 

 exactly how many victims to catch, she cannot attain to counting how many 

 reach their destination, as if the creature had no other guide as to number 

 than an irresistible impulse leading her to seek game a fixed number of times. 



