1972] 
A Icock — Bembix americana 
159 
14. The duration of activity at a burrow and the excavation of se- 
lected nests showed 
that some females constructed burrows with 1, 
2, or 3 cells (Table 
1 ). 
Table 1. The 
number of cells per nest of Bembix 
in Seattle, Washington (1971). 
americana 
A. Excavated Nests 
Duration of Observed 
Number of Cells 
Activity at Nest 
Nests 1-3 
9*, 10* 14 days 
3 
Nests 4 
13 
3? 
Nests 5-10 
8, 8, 9, 9, 9, 10 
2 
Nests 11-13 
2, 4, 6 
1 
Probable 
B. Unexcavated Nests 
Number of Cells 
Nests 14-15 
12, 13 
3 
Nests 16-17 
11, 11 
2-3? 
Nests 18 
8 
2 
Nests 19-20 
7, 7 
1-2? 
Nests 21-22 
4 , 5 
1 
*Nest still active when excavated; third cell contains fly with egg. 
Nest 4 — 3 cocoons located but details of the side burrows were unclear. 
Results 
Table 1 summarizes the results of observation and excavation in 
1971. Two points should be made here. (1) In many cases activity 
at a nest was not seen until the female had begun provisioning a 
cell. This means that the over-all length of activity at some nests is 
underestimated by 2 or 3 days. (2) Throughout the observation 
period weather conditions were such that females were able to work 
for a period of 2 wk or more almost without interruption because 
of rain. 
A variety of nests are illustrated in Fig. 1. Judging from the 2 
cases in which a third cell was found containing a fly and egg, fe- 
males building three-celled nests first dug a more or less straight 
burrow leading to an initial cell. After completion of the provision- 
ing of the first cell, a second one was added by digging a side bur- 
row off at a right angle (more or less) from the main burrow. 
After this cell was dug and fully provisioned, a third burrow was 
constructed off the second cell burrow. This shaft circled back to- 
ward or under the main tunnel with the cell located well under the 
entrance to the nest. 
