What happens when the Queen in a bee hive dies?

If there are still eggs or larvae less than a couple of days old in the brood comb when the workers realize the queen has gone, they can draw a cell out into a queen cell and feed the larva with royal jelly. This will then develop into an new queen. In practice they will probably do this to several eggs.
If there are no eggs, or if the only eggs are drone eggs there will be no bees to replace the current generation and the colony will die out within a month to six weeks.