348 Trans. Acad, Sci. of St. Louis 
for the same purpose, and that distant relatives (Ody- 
nerus) carry water in their throats. These are near 
approaches to the method now discovered, but are not 
its counterpart. When I saw that this P. mellipes re- 
peatedly left the building by a certain crack, and that 
when she returned she was able to gather three pellets 
of reinforcing material, I formed the deduction, based 
largely on experience with Odynerus, that this was 
also a water-carrying species. Yet the puzzling ques- 
tion remained unanswered: If she fills her crop with 
water, how does it go through the body so quickly to 
be emitted from the opposite extremity a few minutes 
later? The drop of water was each time handled with 
such lightning speed that, I must confess, I might have 
been deluded; perhaps the drop came from the mouth, 
and the abdomen was so bent as to whip it instantly 
from the mouth. I craned my neck all the more; I even 
used my magnifying glass, but the work was done too 
quickly for the eye to catch the movements. 
For an hour while the process of reinforeing contin- 
ued, the little mother always went out for water through 
the crack nearest the nest and regularly came back 
through the same crack. Only once did she enter on 
her return through another crack a few inches toward 
the north. Did she go from there to her nest? No, she left 
mmediately by the way she had éome; presently her 
face appeared at the right opening and she proceeded 
direct to her nest and resumed her work. Place mem- 
ory was again demonstrated. 
When at last she seemed to consider her work done 
and failed to return, my attention was directed to the 
behavior of some half dozen other P. mellipes in the puild- 
ing, but of this nest and its contents we shall have more 
to say later. 
