Psyche 
[September 
162 
Table 2. The nest building behavior of marked Bembix americana 
in Seattle, 
Washington (1972) 
First Nest 
Second 
Nest Third Nest 
Wasp 
Duration of Activity 
Cells 
: Activity 
Cells : Activity Cells 
A 
14 days 
(3) 
B 
13 days 
(3) 
C 
10 days 
2E 
5 
IE 
D 
8 days 
2E 
5* 
1* 
E 
7 days 
IE 
9 
2E 
F 
3 days 
IE 
4 
IE 8 (2) 
G 
2 days 
IE 
6 
IE 
H 
3 days 
IE 
12 
2E 
I 
2 days 
(1) 
11* 
2* 
J 
5 days 
(1) 
2 
(1) 
K 
2 days 
(1) 
10* 
2* 
L 
5 days 
(1) 
9* 
2* 
E — nest 
excavated 
( ) improbable number of cells based on length of activity at nest 
* = nest still active when excavated or when study terminated 
Ecological Factors and Nest Design. The significance of variation 
in cell number for digger wasps has not been discussed in great de- 
tail. Presumably there are both advantages and disadvantages asso- 
ciated with the construction of either multi-celled or single celled 
nests. A nest with 3 cells may require the removal of less material 
in building than would 3 separate uni-celled nests. However the 
advantage of reduced energy expenditure in nest building may be 
tempered by ( 1 ) the disadvantage of prolonged activity at one nest 
entrance which may make the individual’s larvae and prey more 
vulnerable to parasites, especially if the latter are capable of learn- 
ing to exploit a specific source of prey and by (2) the disadvantage 
stemming from the possibility of a highly localized disaster which 
would eliminate all the offspring in a multi-celled nest before they 
could emerge (e.g. poor drainage at a particular site). 
If these speculations are correct one would expect multi-celled 
nests in areas where soil conditions or other factors make nest con- 
struction particularly expensive in terms of time and energy costs. 
Evans notes (1966, p. 442) that nests with more than 1 cell are 
more characteristic of species digging in compact soil than those 
which build in sandy soils. Judging from Evans’ account (1957) 
of typical nesting sites for americana the Seattle colony was located 
in an atypically hardpacked and pebbly area. These conditions may 
