Workers are simply underdeveloped queens. They have the ability to lay eggs, but they can only lay unfertilized eggs - which turn into drones. If a hive is without a queen for more than 3 weeks some workers will begin laying eggs. It is usually pretty easy to identify. Workers do not have the ability to control how many eggs they can lay. Their will be multiple eggs and on the cells walls. (They are usually not long enough to reach the very bottom of the cell) You will find