They somehow choose the direction that the foragers will go, and by coming back -- just by making it back -- they tell the foragers that it's safe to go out.
它们设法为觅食的蚂蚁确定方向， 凭着能回巢——就只凭着能会得了巢—— 它们告诉觅食的蚂蚁可以安全外出。