1983] 
Alloway & Del Rio Pesado — Harpagoxenus 
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nests. See Del Rio Pesado (1983) for a complete demographic des- 
cription of the colonies studied. 
In the laboratory, the ants were removed from their natural nests, 
established in artificial nests (Alloway 1979), and censused. Then 
they were transported to a naturally lighted, unairconditioned 
room, where the field maps were used to reconstruct among the 
artificial nests the same spatial relations as had existed among the 
natural nests. In addition to these “natural” quadrants, we also 
observed one control quadrant containing two H. americanus nests 
from different collection sites. In some cases, individual ants were 
marked. See Del Rio Pesado and Alloway (1983) for a detailed 
description of these procedures. 
Ad libitum behavioral observations were made 8 h a day, 5 days a 
week during June, July, and August. Five quadrants were observed 
in 1980; and 14 quadrants were observed in 1981. An assistant was 
employed during 1981 to permit more detailed behavioral ob- 
servations. 
Results 
Raiding 
The slave-makers raided or attempted to raid the nests of ad jacent 
colonies. Most raided nests belonged to unparasitized L. amhiguus 
and L. longispinosus colonies. However, in the control quadrant 
and in the two “natural” quadrants containing more than one H. 
americanus colony, the slave-makers from one colony raided nests 
belonging to another parasite colony. 
Alloway (1979) observed that the raiding behavior of H. america- 
nus is not highly stereotyped even when ants from a single parasite 
nest are interacting with ants from a single target nest. In the present 
study in which the slave-makers were often interacting with ants 
from several naturally adjacent colonies, the results were so com- 
plex and variable that their complete presentation requires a separ- 
ate description of the events in each quadrant. See Del Rio Pesado 
(1983) for such an account. Here we summarize those observations. 
Much of the behavioral variability could be attributed to demo- 
graphic variability. One demographic factor was the number of 
nests in each quadrant. The initial number of slave-maker nests in 
different quadrants ranged from 2 to 6, while the initial number of 
