1983] 
Allow ay & Del Rio Pesado — Harpagoxenus 
435 
slave worker forces may even organize slave-maker colonies in a 
way which produces inefficient raiding. Nevertheless, we doubt that 
any of these behavioral phenomena are manifestations of evolved 
host-species defenses against slave-makers. We suppose that the 
behavior of host-species workers has evolved to maximize the 
reproductive potential of host-species queens. Slave-maker popula- 
tions are so sparse that only a small proportion of host-species 
colonies are ever raided. Thus, slavery seems unlikely to exert signif- 
icant selection pressure on host-species populations; and we believe 
that the facultative polydomy and polygyny found in these host- 
species are adaptations to conditions in host-species (not parasite) 
colonies. 
In these host species, polygyny involves the acceptance of newly 
mated young queens in existing colonies. Simultaneously, poly- 
domy involves a more or less continual exchange of workers, 
queens, and brood among nests; and such commerce requires 
workers in one nest to accept workers, queens, and brood from 
other nests of the same colony (Alloway et al. 1982). An incidental 
effect of these characterstics of host-species colonies is to produce a 
worker caste which is vulnerable to enslavement. Of course, a 
second effect of polydomy is to produce a worker caste which tends 
to organize multiple-nest colonies; and life in multiple nests may be 
disadvantageous to slave-makers. In other words, Harpagoxenus 
americanus parasitizes the labor of workers which possess a “mixed 
bag” of behavioral characteristics. Some of these characteristics 
may facilitate enslavement, while others may produce inefficient 
slave-maker colonies. However, the assertion that host-species 
workers have evolved to be inefficient slaves seems only a little more 
likely than the assertion that they have evolved to be slaves at all. 
Summary 
Colonies of the slave-making ant, Harpagoxenus amerieanus 
(Emery), and two of its host species {Leptothorax anihiguus Emery 
and L. lohgispinosus Roger) were observed under “seminatural” 
conditions, in which the ants lived in artificial nests arranged to 
reconstruct the spatial relationships among their natural nests. 
Some of the slave-maker and host-species colonies were polydom- 
ous.. In some polydomous slave-maker colonies, the slaves carried 
all the H. amerieanus workers into one nest before the onset of 
raiding. When thus assembled, the slave-makers efficiently captured 
