What do bees do at night?
Bees will usually go back to the hive where they will rest. They don't sleep in the same way that humans would, but they do stop their activity and go into a sort of dormant state.
Some bees may have other functions during the night, but primarily most will just return to the hive for some rest.
Bees do not typically fly at night due to the fact they navigate by the sun. If there is a full moon on a clear night or a lot of lights on in a house near to where a colony of bees lives, the worker bees will attempt to work. Bees want to work, so if they since there is daylight by which to work - they will work.
In the night, the bees stay in the hive. However they do not sleep. They need to feed the queen and the larvae, they need to ventilate the hive and get the moisture out so they need to beat their wings continuously to carryout these activities. If you listen to a hive in the night, you will hear the hum of the bees.