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Psyche 
[December 
tion of the bivouac wall with a trowel, and allowing the ants to drop 
into a plastic box. When this method did not yield enough ants, 
we aspirated additional individuals from the area around the nest. 
In the laboratory the ants were kept in a glass aquarium. 
At the start of each day’s test, a petroleum ether extract of whole 
ants was prepared by adding 60 ml of ether to a jar containing 300 
intermediate-sized mature adult ants. A circular trail of the ether 
extract (63 cm in circumference) was deposited on discs of filter 
paper, by allowing the extract to flow out of a microburet suspended 
above a phonograph turntable which was spinning at 78 rpm. The 
ether evaporated in 5 seconds, and in order to observe whether the 
test ants were following the trail, the filter paper was placed upon 
a corresponding circular template. The template circle, as well as 
the lines dividing it into 16 sectors, were clearly visible through the 
discs of filter paper. A new disc of filter paper was used for each 
trial. 
In order to insure uniform orientation of each test ant at the 
start of trail following, a plastic enclosure was used (Fig. 1). It 
Fig. 1. Apparatus used to insure that all test ants initially orient to 
the trail in an identical manner. For explanation, see text. 
