WORKERS IN CLAY 



sionally there is a remarkable innovation in building- 

 material, as where in a group of fifteen, four cells in the 

 centre were constructed of pure white plaster, forming 

 a striking contrast to the surrounding mud color. One 

 wasp built an entire cluster after an original fashion, 

 following the beaten track 

 until the cell was completed, 

 and even bringing mud 

 enough to daub it over, as 

 her sisters were doing, but 

 sticking it all in one spot, so 

 that when the group was horizontal cells of the 



, . , , MUD-DAUBER 



complete irregular lumps 



were attached here and there, leaving visible the elegant 

 architecture of the individual cells. Did she think they 

 were too pretty to spoil ? or was she merely one of those 

 radical spirits that rebel against conventionality and 

 demand change for the sake of change? It is these 

 variations that furnish Natural Selection with its ma- 

 terials; but rigid as may be the rules regarding the 

 non-survival of the unfit, we find that the race of Pelo- 

 paeus still produces many absent-minded wasps, that 

 after spending hours in carefully constructing their 

 nests, seal them up empty, forgetting to put in the 

 spiders or to lay the egg. 



271 



