1983] 
Pesacio & Alloway — Harpagoxenus americanus 
161 
despite the fact that L. ambiguus colonies are generally more 
abundant than L. longispinosus colonies (Alloway et al. 1982). 
Two factors probably account for the prevalence of L. longispinosus 
slaves in H. americanus nests. First, H. americanus seems to mani- 
fest an ecological preference for rather cool, shady places, a habitat 
preference which closely matches that of L. longispinosus. Second, 
at our study site, we found that L. longispinosus nests were on 
average ore populous than L. ambiguus nests. Thus, a raid against 
a nest of L. longispinosus might net more worker pupae than a raid 
against a nest of L. ambiguus. 
Summary 
Field maps were made while collecting nests of the slave-making 
ant, Harpagoxenus americanus, and two of its host species, Lepto- 
thorax ambiguus and L. longispinosus. The ants were then trans- 
ferred to artificial nests arranged to reconstruct the natural spatial 
relationships among nests. Ants from adjacent slave-maker nests 
often exchanged nestmates and brood for a period of time before 
moving into a single nest; and ants which had been living in a single 
nest in the laboratory sometimes moved into two nests. However, in 
other instances, ants from adjacent nests fought. These observations 
were interpreted as indicating that colonies of H. americanus some- 
times occupy more than one nest (facultative polydomy). Nest popu- 
lation data were also presented and discussed. 
References 
Alloway, T. M. 
1979. Raiding behaviour of two species of slave-making ants, Harpagoxenus 
americanus (Emery) and Leptothorax duloticus Wesson. Animal Behav- 
iour 27: 202-210. 
Alloway, T. M., A. Buschinger, M. Talbot, R. Stuart, & C. Thomas. 
1982. Polygyny and polydomy in three North American species of the ant 
genus Leptothorax Mayer (Hymenoptera: Formicidae). Psyche, 89: 
249-290. 
Bhatkar, a. & W. H. Whitcomb. 
1970. Artificial diet for rearing species of ants. Fla. Entomologist 53: 217-232. 
Buschinger, A. 
1978. Genetically induced origin of alate females in the slave-making ant, Har- 
pagoxenus sublaevis (Nyl.) (Hym., form). Insectes Sociaux 25: 163-172. 
Buschinger, A., & T. M. Alloway. 
1977. Population structure and polymorphism in the slave-making ant Harpa- 
goxenus americanus (Emery). Psyche 83: 233-242. 
