XXII AN EXCHANGE OF NESTS 315 



most absurd way, — by breaking into another bee's 

 cell, continuing to store in a cell already overflowing, 

 placing an egg where the real owner had already 

 laid one, and finally, closing an orifice which needed 

 serious repairs. Could one desire a better proof of 

 the irresistible impulse obeyed by the insect ? 



Finally, there are other rapid and consecutive 

 actions so closely connected that the execution of 

 the second implies necessarily the repetition of the 

 first, even when this has become useless. I have 

 already said how Sphex flavipennis persists in going 

 down into her burrow alone, having brought near it 

 the cricket which I cruelly removed immediately. 

 Her repeated discomfitures did not make her give up 

 the preliminary domiciliary visit, useless as it is 

 when repeated ten or twenty times. Chalicodoma 

 muraria exhibits under another form a like repetition 

 of an act useless itself, but a necessary prelude to 

 the next one. Arrived with her booty, she goes 

 through a double act of storage. First she plunges 

 head first into the cell to disgorge the contents of 

 her crop ; then she comes out, returning at once 

 backward to brush off her load of pollen. At the 

 moment when she is about to enter, tail first, I 

 gently put her aside with a straw, thus hindering her 

 second action. She begins all over again, going 

 head first into the cell, although her crop is empty. 

 Then comes the turn of going in backward, I 

 instantly put her aside again, and again she goes in 

 head first. Once more I use my straw. And this 

 goes on as long as the observer pleases. Put aside 

 just as she is about to introduce her hinder parts 

 into the cell, she returns to the orifice and persists in 



