BLACK REED WASP 399 



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 maxi- 

 mum 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 contains twenty spiders separated into three little 

 groups by half partitions of clay. Upon the abdomen of a 

 large spider in each group she has deposited an egg. Now 

 I close the box and await her return. She arrives laden with 

 a tiny ball of clay in her mandibles, enters the nest for a mo- 

 ment and then flies off minus her burden. 



At the end of an hour the operation has been repeated 

 twenty times. Now she commences to close the entrance 

 with the same material. The job requires ten more loads of 

 mortar, but it is completed rapidly. By evening she has left 

 the nest, I presume for good and all, and for the last time 

 I pry into her secrets. 



It is all very clear. In a single day she has accumulated 

 the entire amount of provision necessary to provide her three 

 offspring and separated them into distinct groups. Further 

 she has constructed half partitions that keep the stores sep- 

 arate, but still permit her to pass from one end of the nest 

 to the other. Thus she is enabled to deposit her three eggs 

 in different departments of the nest, all on the same day. 

 The laying over, she has only to finish the half partitions 



