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[Vol. 90 
their broods (Wesson 1939; Buschinger & Alloway, 1977). In the 
related European slave maker, H. sublaevis, “ergatoid queens” 
(individuals with fully functional ovaries and a spermatheca, but 
with a more or less worker-like external morphology) are common 
and function as the usual female reproductives (Buschinger, 1978). 
However, Buschinger and Alloway (1977) found that, while many 
H. americanus workers have functional ovaries and lay eggs that 
can mature to produce males, they rarely, if ever, possess a spermat- 
eca. Thus, “ergatoid queens” are absent or very rare in H. ameri- 
canus. Moreover, these authors thought that thelytoky was unlikely 
in this species. 
Wesson (1939) observed the formation of secondary nests in the 
laboratory. Slave-maker colonies which had conducted several 
ordinary slave raids sometimes concluded the final raid of the sea- 
son by splitting into two components. In these cases, a few slave- 
maker workers and slaves remained indefinitely in the raided nest 
with part of the captured brood. Wesson suggested that this might 
be a sufficiently common late-season activity to account for the 
frequent occurrence of secondary nests. However, even if secondary 
nests are formed in this manner, there are still two possibilities for 
the relationship between secondary and primary nests and for the 
origin of the female slave-maker brood in secondary nests. Follow- 
ing their formation, secondary nests might become autonomous 
entities functionally separate from their parental primary nests. In 
this case, if we exclude thelytoky, the female slave-maker brood in 
secondary nests would have to be derived exclusively from brood 
carried over from the primary nest when the secondary nest was 
initially occupied (Buschinger & Alloway 1977). Alternatively, the 
primary nest and one or more secondary nests might comprise a 
single multiple-nest (polydomus) colony (Sturtevant 1927). Interac- 
tions between the nests of such polydomous colonies would be pro- 
tracted, and the slave-maker queen would continue to supply female 
brood for all nests in her colony. The latter possibility is supported 
by the fact that polydomy of this type has recently been demon- 
strated in two of the host species of H. americanus, Leptothorax 
ambiguus Emery and L. longispinosus Roger (Alloway et al. 
1982). The objective of the present study was to examine these two 
possibilities by collecting and mapping H. americanus and host- 
species nests in nature, reconstructing their spatial relationships in 
the laboratory, and observing the interactions among them. 
