1968] 
West — Polistes exclamans 
119 
the present Beaumont Reservation, 18 miles southwest of St. Louis, 
the former site of some “woodcutters’ cabins” often visited by Rau 
during the years 1945-1947 (Rau, unpublished manuscript). * 1 
There is little doubt that Rau would have noticed and reported 
P. exclamans in the St. Louis region if the species had been present 
there during his lifetime. He published 39 papers and one book 
chapter (Rau and Rau, 1918) on the Polistes of 43 named localities 
in that area during the years 1918-1946, and devoted his last years 
to writing a book dealing exclusively with the bionomics of Polistes 
(Rau, unpublished manuscript). Furthermore, Rau would have 
been unlikely to confuse exclamans with any of the Missouri species 
he recognized, since it has a distinctive appearance and nest form 
appreciated and described by Rau when he collected it in Texas 
(Rau, 1943). Therefore it seems reasonable to conclude that the 
present abundance of Polistes exclamans in southern St. Louis County, 
Missouri, is due to colonization in that area during the last twenty 
years. 
Examination of museum collections (see Acknowledgments) has 
revealed specimens of P. exclamans from nine states not considered 
part of the species range in 1951 (Bohart, 1951) (Table 1). Eight 
of the new state records are in the northeastern quarter of the species 
range, suggesting a generally northward expansion in the eastern 
half of the United States. Since climate-related range fluctuations are 
quite common in animals, and there are numerous examples of north- 
ward expansion in North America during the present century (see 
Mayr, 1963), climatic change and/or adaptation to more northern 
habitats must be considered as possible contributing factors in the 
expansion of P. exclamans. However, there are pre-1950 records of 
P. exclamans from northern Kansas, Nebraska, and Iowa — north 
of all the new records (Table 1) — suggesting that the expansion 
may not bear a simple relationship to climate. 
A possible behavioral basis for range expansion in P. exclamans was 
suggested by field observations of newly founded Polistes colonies on 
and near the University of Oklahoma Biological Station (Marshall 
County, Oklahoma). Nests of P. annularis , P. apachus , P. fuscatus, 
P. metricus and P. rubiginosus observed between 20 April and 11 
May, 1966, were commonly attended by more than one female 
(foundress). However, each except one of more than 100 P. ex- 
clamans colonies was attended by a single female; the one exception 
had only two foundresses. Solitary nest founding 2 predominated even 
Thil Rau’s son, Mr. David Rau, kindly helped in locating these sites. 
I prefer this term to the older “haplometrosis” or “monogyny”, and the 
term “social nest founding” to “pleometrosis” or “polygyny”, for reasons 
given in West, 1967b. 
