After getting many calls for queens lately. The culprit for the calls has been late season swarming. It seems that the warm weather, a little rain and fully mature hives equals a swarm. Most beekeepers haven't seen the swarms. But from checking their colonies have discovered no eggs. By rushing to judgment and wanting to throw in a queen can backfire. In most cases swarm cells produced a virgin queen that has to mature to a laying queen. This may take three weeks to a month before new eggs are seen again in the colony.
If a new queen is thrown in the hive without checking for an open swarm cell. The new queen that the beekeeper has plopped down 30 bucks for is quickly killed by the virgin queen or the bees in the hive.
The first thing I do if I have a queenless hive in July or August is take a frame of eggs from another colony(this is the reason to have two colonies). After about 5 days or so I stop back to look at that frame. If the bees have started to make queen cells on this frame it is safe to assume that the hive is queenless.
If no queen cells are being produced the hive is normally queenright but the queen has not started to lay yet. This works great also to buy time for the hive from turning to laying workers while the beekeeper figures out what is going on in the hive. A frame of eggs that will turn to brood then capped brood will delay laying workers from developing in a colony as long as brood is present.