456 Trans. Acad. Sci. of St. Lours 
turning a moment later, removed these spiders. Since 
the meddling here had been more extensive than usual, 
I was not surprised that she resented the intrusion, but 
I cannot understand what caused her great confusion 
in finding the nest when the alterations in the surround- 
ings were imperceptible to me. 
Exp. XI. ‘A solitary cell contained five spiders when 
I added six more from another nest. The wasp re- 
turned empty-handed, put her head into the cell and 
worked energetically for three minutes, either inspect- 
ing or packing them together or laying her egg. Out 
she came at last and dashed away, but without a spider; 
almost immediately she returned with her plaster and 
sealed up the cell. 
When she had gone, I broke the seal and removed part 
of the spiders which she and I had together supplied. 
She soon returned with another pellet of mud to add 
to the seal, but when she found it broken she alertly 
poked her head in, hastily withdrew and flew away with 
the mud. After that she made four trips from the nest, 
each time carrying out a spider which I had failed to 
remove, but these four were those which she herself had 
put in. Then for ten minutes she thoroughly examined 
the inside and outside of the cell, going in and out many 
times, apparently in an earnest attempt to discover the 
cause of the mysterious trouble. When I returned that 
afternoon, I found her again filling this cell with spiders. 
During her absence I again meddled, this time insert- 
ing twelve spiders from another nest. Returning, she 
brought a spider which she crammed in on top of the 
others, and departed. After ten minutes, however, she 
came buzzing back as if possessed of a new idea, and 
began to empty the cell! First she took out her ow? 
fine fresh one and threw it away, and continued until 
