Figure 1.

Experimental set-up. In experiment 1, either a free flow of ants was allowed to and from the feeder, or only the first seven to nine ants to find the feeder were allowed onto the walkway, the rest being excluded by only lowering the drawbridge as a marked ant approaches it. The walkway was either narrow (5 mm) or wide (20 mm). A mirror placed by the walkway at 45° allows the ants to be observed from above and the side simultaneously. In experiment 2, 10 glass beads, either black or clear, either coated in nest-mate cuticular hydrocarbons or not, were evenly spaced along the walkway, which was 5 mm wide. As a negative control in experiment 2, no beads were placed on the walkway. (Online version in colour.)