102 Psyche [March 
Aggressiveness Toward Cofoundresses 
Unilateral aggressiveness is evident even before colony initiation. 
Much like the behavior of P. gallicus (L.) (Pardi, 1948), there is 
a lack of equivalence between females, certain females apparently 
showing dominant characteristics from the start. Likewise, a female 
that appears dominant never loses her dominant position on the nest. 
Females attack each other in the pre-hibernation and early post- 
hibernation clusters (Hermann and Dirks, 1975). Such aggressive- 
ness may involve a rapid darting of one female toward another. In 
many cases, aggressive attacks result in the entanglement of a wasp’s 
legs with those of the other wasp and the subsequent falling to the 
ground by these individuals while attempting to bite and sting. 
On occasion, we have found individuals that were stung, although 
most encounters merely result in some establishment of dominance 
by one of the fighting pair without bodily harm. Both wasps most 
often take flight after such an encounter and either return to the 
cluster (in the case with the dominant wasp and often the subordi- 
nate one also), or retreat to a new location. As with P. canadensis 
(Eberhard, 1969), subordinate cofoundresses that actually were at- 
tacked by the dominant female often left the colony. Subordinate 
P. canadensis females that remained on the nest became idle residents ; 
however, subordinate P. annularis females became workers (beta 
individuals of Pardi, 1948). 
We believe that the females remaining in these clusters are the 
ones that commence a pleometrotic colony while the most subordinate 
females (the ones that fly away from the clusters) often establish 
small colonies as single queens, sometimes later to be joined by other 
cofoundresses. In most cases, females that initiated their nest build- 
ing alone never completed their nest; the nests never got to be larger 
than a few cells and the nests eventually were abandoned. 
During colony initiation, subordinate females that initiate their 
own colonies singly are occasionally replaced by new dominant fe- 
males that arrive after a small nest with several cells has been con- 
structed. On occasion, we have even seen P. annularis queens re- 
placed by a P. ex damans queen (possible beginning of an allometrotic 
association), although colony life ceases to function when there is 
such an aggregation of two species. 
In other cases, nests with single or multiple foundresses may pick 
up additional females that come from other nests. In the latter case, 
these females either come from nests that they were chased from or 
from a nest of sibling females ( females that originated from the same 
