248 PHIL RAU 



added five from another nest. The wasp returned, carrying 

 another spider which she crammed into the cell, while with her 

 head she condensed the whole mass. In so doing she somehow 

 dislodged one and it fell into the spiderweb below; she alertly 

 recovered it, crammed it into the cell with precision and con- 

 tinued to pack the mass together for about five minutes, then 

 flew out and brought one more spider which she deposited, 

 almost filling the compartment. 



When she had gone again I forced five additional spiders 

 into the cell ; after a half hour she returned with another capture 

 which she also forced in with great effort. It seemed that she 

 had a fairly definite idea how many spiders were required, and 

 bring them she must and would, regardless of unsolicited aid. 

 In this she differed from other individuals of her species, in whom 

 the sight alone of few or many spiders in the cell was sufficient 

 stimulus to induce the sealing process. 



But upon her next return she brought a load of mud and 

 closed the cell. When she was gone I opened it and removed 

 one-third of the spiders. The next load of mud was used in 

 precisely the same way; absolutely no attention was paid to 

 the broken cell or the missing spiders. Again I removed the 

 seal and all of the spiders in order more forcibly to impress 

 upon her the seriousness of the injury. I accidentally broke a 

 small piece out of the wall of the cell at the opening. The wasp 

 returned, spread her mud over the opening, leaving the broken 

 part untouched and quite ignoring the emptiness of the nest 

 or the traces of vandalism. She discharged her duty always 

 with a mechanical faithfulness; she seemed, nevertheless, exact — 

 three loads of mud are usually required to seal a cell, and three 

 loads she brought and applied properly before finally leaving 

 the nest. 



Exp. 19. When I arrived upon the scene the fourth cell of a 

 Pelopoeus nest was half filled with spiders. Not having other 

 spiders at hand, I placed a pupal case containing a pupa of the 

 same species in her cell so that no part protruded. When I 

 returned two hours later the cell was sealed and a fifth cell of 

 the nest half completed. I had to break open the cell to see 

 if the pupa had been removed. The cell was quite empty, but 

 the new item of interest was that at six the next morning I 



