Food-deprived colonies were given access to a maze with a large
1 M sucrose solution feeder at the opposite end. The maze consisted
of two parallel paths, 10 mm wide and 200 mm long, joined
at each end by a 90 Y-bifurcation with 40 mm long arms (see
Fig. 1), thus forming a stretched hexagon. The maze and all other
parts of the apparatus to which the ants had access were covered in
disposable paper overlays. Equal numbers of black glass beads,
either uncoated (control beads) or coated with nestmate CHCs
(dummy ants), were placed on both paths. The first 10 ants to reach
the feeder were marked with a dot of acrylic paint on the abdomen,
so as to allow the behaviour of individual ants to be followed on
their first return trip to the nest. The ants were then allowed to
forage undisturbed for 1 h, during which the entire maze was
filmed in high definition from above using a Sony Handycam
CX190. From these videos we obtained information such as the
number of ants on each path at various times, the time at which the
first ants began returning to the nest and the number of U-turns. At
the end of the experiment all marked ants were removed from the
colony, the remaining ants returned to the nestbox, the maze
cleaned with ethanol and the paper overlays replaced. Both control
beads and dummy ants were discarded after every trial.