THE BLACK REED-WASP 31 



entrance will naturally receive the first provisions collected, and, it 

 would seem, in due time, the first egg deposited. The remaining 

 two cells would receive their respective contents in the order of their 

 position, but the first egg laid, naturally hatches before the others. 

 The grub reaches maturity, pupates and is ready to emerge some- 

 time ahead of its sisters in the other cells. What happens then? Does 

 the issuing wasp burrow its way out through the cells in front, up- 

 setting in its passage the vital conditions of solitude that surround the 

 younger insects? Does it burrow through the clay plugs, separating 

 each nursery, and as a final act of vandalism, leave the nest open, 

 exposing its younger sisters to the first parasite? 



So it would seem, but such a course would be contrary to all the 

 laws of nature. She does not destroy her children needlessly, yet I 

 wonder what happens in such nests as that of the black reed-wasp, 

 whose oldest child seems farthest from the door to freedom! 



Perhaps the parent wasp is gifted with the power of laying eggs 

 that require varied terms of incubation. In the first cell provisioned 

 she lays an egg that requires three days to hatch, in the middle cell 

 one that requires two days and in the outer cell the egg hatches in a 

 day and a half. The theory would straighten out the difficulty 

 very nicely. The insects would emerge in turn without disturbing 

 one another and all would be well, but a theory is no better than a 

 guess. Moreover a little careful observation of the glass tubes yields 

 the correct and simple answer to the question. 



I watch a wasp entering one of the tubes carrying a spider which 

 is held tightly beneath her body. She enters, stores the game, 

 squeaks about it to her watching mate, and is off again in search of 

 a second victim. She does not rest after placing eight spiders in the 

 tube, yet this is the maximum number for a single cell. Instead, 

 the work continues during most of the day without interruption. 



In the afternoon I open the box containing her nest. The tube 



