MUD-DAUBING WASPS 121 



the females too like to loaf sometimes. On September 16, 

 1914, we observed one mother at work during the afternoon. 

 At 3: 15 the cell was completed but unsealed and unfilled, 

 and the wasp was bringing mud to reinforce the nest, by 

 spreading it thin all over the outside. Up to 7 o'clock she 

 was still thus occupied without paying any further attention 

 to the unfilled cell. Until noon the next day the wasp was 

 absent, possibly loafing. At 4 o'clock when we returned to 

 the nest we found that the cell had been filled and sealed in 

 the interval, but further work for the day had been discon- 

 tinued. We watched for her the remainder of that after- 

 noon and all the next day, but there was no return whatso- 

 ever to the nest. On the following day also we lay in wait 

 for her, and were about to give her up as dead, lost or 

 stolen, when she returned for an hour at midday and fin- 

 ished another cell, after which she seemed to consider her- 

 self deserving of another afternoon off. Unfortunately we 

 could not watch her beyond this time, but we have often 

 wondered if this was an unusually indolent individual, or if 

 such is about the usual rate of progress of the work of 

 these wasps. 



The nests of this mud-dauber and those of Chalybion 

 coerideum are identical. Figure 30 illustrates the exterior 

 and interior of their homes. Some nests show nicely the de- 

 tails of architecture (upper figure), while in others these de- 

 tails are obliterated by the decorations of mud pellets (see 

 middle figure). 



A six-celled nest of a P. caementarium was found hanging 

 firmly to a root only two mm. in diameter which ran along its 

 longitudinal axis. It reminded us of the mode of attach- 

 ment of the potter wasp's cell to the twigs of plants. This 

 was the root of an overturned tree on the top of a sand- 

 bank ; the soil was washed away from the roots, and on one 

 of these strands of exposed rootlet this nest was very deftly 



