196 
Psyche 
[Vol. 90 
paring her nest a female would sit quietly at the back of the stick or 
just inside the entrance for a few minutes to an hour. Once a choice 
was made, extraneous pith particles were picked up with the man- 
dibles and Jettisoned outside of the nest during flight. Females did 
not make the nest walls completely smooth but cut away gross 
irregularities with the mandibles and removed large pith particles. 
As many as 24 pith removal trips were observed before nest initia- 
tion. During this period of preparation females were especially sen- 
sitive to any activity around the nest site. On several occasions 
females abandoned nests when an observer approached the nest 
entrance. In general nesting E. pugnata were very wary of intruders. 
Partition Building. Basal and apical partitions of each cell were 
constructed similarly and were composed of the same materials so 
construction details of each will be considered together. 
After preparing her nest site for cell construction the female left 
the nest to retrieve a strip of O. hookeri leaf. The bee landed on the 
plant, straddling the leaf, and quickly cut, while walking backwards, 
a thin strip V 2 to Ya, as long as her body, and returned to the nest. 
After entering the nest with the unmodified leaf in her mandibles the 
female masticated it into a shiny ball which was pressed into the 
back wall, or along the floor where the cell was to be initiated. From 
the leaf material a thin ring of moist chewed leaf was formed around 
the inner circumference of the tunnel. Three to 6 trips were usually 
required to complete the ring. The female then left and returned 
with a large oval-shaped leaf piece that was carried beneath the 
body by all 6 legs and the mandibles. 
The mandible and front legs were used to spread and position the 
leaf piece along a portion of the chewed ring thus closing a portion 
of the circle (Fig. 2). The outer edge of the unmodified leaf confluent 
with the ring was chewed into the ring and the 2 were sealed. The 
female also used her head in an extremely fast jackhammer-like 
motion to tamp the ring and leaf pieces together. The clypeus and 
proximal outer surfaces of the mandibles appeared to be the point 
of impact. Subsequent leaf pieces were brought in and fastened to 
the ring in the same manner until the base of the cell was covered 
(Fig. 2). Three or 4 oval-shaped leaf pieces were required to form the 
base of the partition. After the leaf pieces were positioned more 
masticated Oenothera strips were used to form a second ring in the 
