1983] 
Pesach & Alloway — Harpagoxenus aniericanus 
153 
Material and Methods 
The ants were collected on the Erindale Campus of the University 
of Toronto in Mississauga, Ontario, during the spring and summer 
of 1980 and 1981. Since our purpose was to determine whether 
colonies of H. americanus sometimes occupy more than one nest, 
we looked for areas where two H. americanus nests occurred within 
2 m of each other. Whenever such a place was located, we layed out 
a 2 m by 2 m quadrant centering on the two nests and then collected, 
numbered and mapped the location of every H. americanus nest and 
every nest of its host species (L. ambiguus and L. longispinosus) in 
the quadrant. In some cases, adjacent quadrants were combined to 
permit the collection of a larger group of slave-maker nests. 
In the laboratory, we removed the ants and their brood from their 
natural nests and established them in artificial nests of the type 
described by Alloway (1979). For censusing, the artificial nests were 
placed in petri dishes (diameter = 14.5 cm; height = 1 .5 cm) contain- 
ing a water bottle and food (Bhatkar & Whitcomb 1970). Then the 
ants were transported to an unairconditioned, naturally lighted 
room. On the floor of this room, quadrants were layed out with 
masking tape; and the field maps were used to locate the position 
occupied by each nest. A thick layer of petroleum Jelly on the mask- 
ing tape formed a barrier which confined the ants to their respective 
quadrants. A water bottle and food were placed near each nest. In 
this way, it was possible to set up the artificial nests so that we 
duplicated the spatial arrangement of the natural nests. 
In addition to the quadrants collected from the field, we set up 
one control quadrant to study behavioral interactions between two 
H. americanus nests which had not been collected near one another 
in nature. The sides of this control quadrant were 100 cm long, and 
the two nests were placed 80 cm apart. 
During the course of our observations, some of the ants were 
marked so that they could be individually identified. Each mark 
consisted of a very small dot of colored nail polish applied to the 
dorsal surface of the gaster with the tip of a minuten pin embedded 
in the end of a wooden stick. Ants remained marked for periods of 1 
day to 1 month. 
Observations were made 8 h a day, 5 days a week between 10 June 
and 27 August 1980 and between 7 May and 30 August 1981. Five 
quadrants were collected and observed during 1980; and 14 quad- 
rants were collected and observed during 1981. 
