Field Studies of the Non-Social Wasps 355 
The wall-structure of this Sceliphron nest had not 
been reinforced in the usual way; consequently it was 
thin and quantities of it were required to make the com- 
pact cell of P. mellipes. Hence the tops of three large 
cells had been demolished and much additional material 
taken from the other two cells, to put into the making 
of the three stocky little cells which had been built with- 
in the one chosen mud-dauber’s cell. 
The P. mellipes builder did not each time return direct 
to one spot to get her mud, but walked all over the nest 
in a searching attitude, sometimes more than once, be- 
fore stopping to get her mouthful. Sometimes she went 
to the same place on two consecutive trips, but more 
often she landed at a new spot each time. ‘At about 6 
0’clock the cup-shaped cell was completed very near to 
the opening, and the next few loads brought in were used 
to fill in the niches about the new cell. When she left 
at 6:08 and did not return at the usual time, I suspected, 
since her nest seemed completed, that she had gone in 
search of a spider. I waited until 7 p. m., when it was 
quite dark in the shed, but she did not return. Occa- 
sional visits during the two days following showed me 
no evidence of the return of the mother. Perhaps she 
had met with a tragedy; perhaps I had frightened her 
away by trying to observe the progress of her work by 
the aid of lighted matehes. The cell which she had 
completed before her disappearance was found to be 
empty ; the middle one contained a spider, Phidippus sp. 
[J. H. Emerton], and had a discolored egg fastened 
across the dorsal surface of the abdomen. The remain- 
ing cell, the oldest of the three, contained an almost full 
8rown P. mellipes larva and a few fragments of spiders. 
It was replaced and on September 24 it spun its cocoon. 
