164 
Psyche 
[September 
Summary 
Females of a population of Bembix americana built complete nests 
with 1, 2, or 3 cells at a site in Seattle, Washington. This is only 
the second report of variation in cell number for this well-studied 
species. Marked individuals generally built single-celled nests at 
the start of the season with subsequent nests likely to be multi- 
celled. Speculations on the adaptive significance of multi-celled nests 
and the pattern of nest building observed in Seattle are presented. 
Acknowledgments 
I am especially grateful to Dr. Howard E. Evans for his kind- 
ness in identifying the wasps, suggesting ideas for research, and 
reading an earlier draft of this paper. Virginia Anderson made a 
number of useful observations at the nest sites after I left the Seattle 
area and I thank her for her help. This work was done while the 
author was supported by NSF grants GB-28714X, GB-28714X1, 
and GB-35269. 
References 
Evans, H. E. 
1957. Studies on the comparative ethology of digger wasps of the 
genus Bembix. Cornell University Press, Ithaca, N. Y. 
1966. The comparative ethology and evolution of the sand wasps. 
Harvard University Press, Cambridge. 
Evans, H. E. and R. W. Matthews 
1968. North American Bembix , a revised key and suggested group- 
ing. Ann. Entomol. Soc. Amer. 61: 1284-1299. 
Parker, J. B. 
1925. Notes on the nesting habits of Bembix comata Parker. Proc. 
Entomol. Soc. Wash. 27: 180-195. 
