Ants in the raft that have more than 2 links to other ants or the bridge do not disengage. The ants on the outside with two or fewer links are the ones that disengage and walk atop the raft to the bridge. This behavior unloads the raft from the side opposite the bridge and maintains the link between raft and bridge.
A queen will only leave the raft after a suitable number of workers have established on dry land. The queen is the most valuable ant on a raft. By leaving the raft in the middle of the process, a queen will always be surrounded by defenders. The last individuals to leave are those that are connected directly to the bridge.
This orderly process, governed by simple behaviors of the individual ants, ensures the safe relocation of the queen and the maximum number of workers.