52 
Psyche 
[September 
as a result nests containing several cells often have a very large mound 
of earth (as much as 3 cm. high). It was our impression that indivi- 
duals that level following completion of the initial cell also level 
after each additional cell, but our data on this point are weak. 
When the nest or new cell is completed, and leveling is completed 
if this is to occur, the female flies off to obtain her first fly, on which 
the egg is laid. This invariably occurs in the late afternoon or early 
evening, and after oviposition the female closes the nest from the in- 
side for the night. Thereafter the nest entrance is left closed from the 
inside when the female is inside for long periods of time (at night and 
during much of the day). During these periods the cell is also closed 
off from the burrow by a small barrier of sand. The female remains 
in the bottom of the burrow just outside this barrier or “inner closure”. 
During periods of provisioning, however, both inner and outer close- 
ures are removed. Nest entrances are occasionally found to be open 
for brief periods in the morning, probably while the female is out 
taking nectar from flowers. In this area no wasps were actually ob- 
served visiting flowers. Final closure of the nest is not especially 
distinctive and has already been described (Evans 1957) * 
Description of nest . — - The burrow measures about 15 mm. in 
diameter, generally slightly more than this near the entrance. It enters 
the soil at a 45-70° angle with the horizontal but tends to level off as 
it approaches the horizontal cell. The burrow is often straight but 
may have a weak to strong lateral curve part way down. Measure- 
ments of 36 nests showed the burrow length to vary from 19 to 40 
cm., with a mean of 30 cm. Depth of the bottom of the cell, measured 
vertically from the soil surface, varied from 10 to 22 cm., with a 
mean of 15 cm. Cells measured about 18 mm. in diameter and from 
30 to 40 mm. in length. 
Of 16 nests dug out May 8-1 1, 1958, 14 contained one cell and two 
contained two cells; none of these nests had yet received the final 
closure and hence all might have eventually had additional cells. Of 
20 nests dug out by C. S. Lin June 4-7 of the same year, 1 1 contained 
one cell, 8 contained two, and one contained three. Only a few of 
these (including the three-celled nest) had received the final closure. 
The several nests dug out in late June, 1956, were nearly all multi- 
cellular (Evans 1957). Two nests were tricellular; one of these was 
still active while the other was receiving the final closure when dug 
out. Two other nests appeared to have four cells and another five. 
However, in these cases all the cells contained cocoons and the burrows 
