178 THE SOLITARY WASPS. 



patting it both inside and outside as the wall grows. The lay- 

 ers are put on in a more or less oblique position, and each load 

 makes about half a ring in the larger parts, or a whole ring 

 near the bottom of the cell. From thirty-two to forty loads 

 complete the cell, which is composed of from sixteen to twenty 

 layers. As a usual thing one cell is placed against another 

 until a large mass is formed. The wasp adds nothing to the 

 mud, depending upon its drying for the necessary firmness, and 

 if, by some accident, the rain strikes it the whole becomes soft 

 and falls to pieces. Since one wasp builds in several different 

 places in a summer it is difficult to say what should be con- 

 sidered a fair amount of work for a season. Most commonly 

 there are five or six cells in a group. The largest number 

 that we have ever found was twenty-one. Probably we should 

 have found the average number higher if we had not collected 

 while the work was still going on, instead of waiting until the 

 season was over. 



The cells, when first finished, are elegant affairs, and with 

 the blue or yellow wasp standing on the rim, they present a 

 very pretty picture ; but soon all this is changed, for when a few 

 cells are done she brings pellets of mud and plasters them all 

 over the outside, hiding the contour of the rings and making it, 

 in very truth, the nest of a dauber. What it loses in beauty, 

 however, it gains in durability and strength, and as the later 

 cocoons must remain within through the winter we will hope 

 that the thickness, of the walls serves as a protection when the 

 mercury goes down below the zero point. One wasp had too 

 much artistic sense to spoil the appearance of her work, but she 

 compromised with her instinct by bringing the extra amount of 

 mud and attaching it in lumps here and there over the whole 

 of the group (PI. X., fig. 1.) We, ourselves, preferred this 

 style of architecture to the other. The chief interest of Pelo- 

 paeus lies in instances like this, of marked variation in an im- 

 portant instinct. 



Almost all the cells that we have collected during the past 



