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Psyche 
[Vol. 90 
Nevertheless, the fact that ants which had been living in several 
different nests in nature so frequently moved into a single artificial 
nest in the laboratory is somewhat problematic. Under our labora- 
tory conditions, polydomy seldom persisted, possibly because our 
artificial nests were somewhat more spacious than the acorn nests 
which these ants inhabit in nature. If the ants live in more than one 
acorn because no single acorn is large enough for the whole colony, 
then giving the colony a larger artificial nest might produce nest 
fusion. However, many factors other than space may be involved in 
producing and maintaining polydomy in these ants (see discussion 
in Del Rio Pesado, 1983). 
Our observations of nest divisions in two quadrants further sup- 
ports the polydomy hypothesis. However, the nest fusions which we 
saw did not closely resemble those described by Wesson (1939). In 
only one of our colonies did raiding parties tend to remain in target 
nests; and even these raiders returned home after 1 to 3 days. What 
we observed was that ants which had been occupying one nest came 
to occupy two nests after the “raiding season” was over. 
Several previous investigators have noted that many H. ameri- 
canus nests are queenless (Buschinger & Alloway 1977; Creighton 
1927; Sturtevant 1927; Wesson 1939). The usual conjecture has been 
that most of these queenless nests are “branches” located near 
queenright nests. Our data confirm this supposition by showing that 
many queenless nests are parts of queenright polydomus colonies. 
However, there were 7 quadrants in which we could not find a nest 
containing an H. atnehcanus queen. Since these queenless nests 
produced only male slave-maker brood, it is unlikely that they 
represent components of a queen-right polydomous colony; and the 
males produced in these nests are probably the offspring of H. 
aniehcanus workers (Buschinger and Alloway 1977). Some of these 
isolated nests may be remnants of colonies whose queen has died, 
while others may be products of long-distance raids from which the 
raiders failed to return. The presence in some H. americanus nests of 
slaves belonging to a species for which there were no free-living 
nests in the same quadrant suggests that H. americanus raids may 
occur over distances of several meters; and far-ranging raiders may 
sometimes fail to return to their base (Creighton 1927). 
In our study area, L. longispinosus slaves outnumbered L. ambi- 
guus slaves by a ratio of almost 4: 1 . This finding is typical through- 
out southern Ontario and the adjacent parts of New York state, 
